[NativeAOT] Fix application linking with API level > 21

[grendello]

Context: bef768d
Context: dotnet/runtime#124461

Follow up to bef768d which puts the non-mono builds API level in
several more locations throughout the source. This is necessary for
NativeAOT builds to correctly link as they must use the same API
level .NET for Android was built with. Failure to do so may result
in missing native symbols when linking.

NativeAOT builds now use full path to the linker (in our case clang++)
and pass the --target=${ARCH}-linux-android${API} argument to it, just
like the toolchain wrapper scripts in the NDK do. Without the parameter,
the lowest supported API level will be used (currently 21).

[Copilot]

Pull request overview

This PR updates the .NET for Android NativeAOT build/link pipeline so that non-Mono (NativeAOT/CoreCLR) builds consistently use the same Android API level that the runtime pack was built with, avoiding missing native symbols at link time (especially when targeting API > 21).

Changes:

• Add “non-mono” NDK API level placeholders and propagate them into generated MSBuild props/projitems.
• Update NativeAOT linking to use the NDK’s clang++ via full path and pass an explicit --target=${ARCH}-linux-android${API} linker argument.
• Split minimum-supported API metadata for arm64/x86_64 based on runtime flavor.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.props.in	Adds non-mono API level properties and runtime-conditional minimum API items (currently with issues).
src/Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.targets	Wires new placeholder replacements into Common.props generation.
src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets	Uses NDK clang++ full path and adds --target=... to linker args.
build-tools/xaprepare/xaprepare/Steps/Step_GenerateFiles.cs	Adds new placeholder values for non-mono API levels when generating Ndk.projitems.
build-tools/scripts/Ndk.projitems.in	Introduces properties/metadata for non-mono API levels for arm64/x64.

[jonathanpeppers]

There are some errors building NativeAOT projects like:

gcc : error : unrecognized command-line option '--target=x86_64-linux-android21' [C:\a\_work\1\a\TestRelease\02-13_14.27.07\temp\BuildApplicationAndCleanTrueapkNativeAOT\UnnamedProject.csproj]
         gcc : error : unrecognized command-line option '--target=x86_64-linux-android24' [C:\a\_work\1\a\TestRelease\02-13_14.27.07\temp\BuildApplicationAndCleanTrueapkNativeAOT\UnnamedProject.csproj]
         C:\Users\cloudtest\.nuget\packages\microsoft.dotnet.ilcompiler\11.0.0-preview.1.26076.102\build\Microsoft.NETCore.Native.targets(391,5): error MSB3073: The command ""gcc" "obj\Release\android-x64\native\UnnamedProject.o" -o "bin\Release\android-x64\native\UnnamedProject.so" -Wl,--version-script="obj\Release\android-x64\native\UnnamedProject.exports" -Wl,--export-dynamic -gz=zlib -fuse-ld=lld C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libSystem.Native.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libSystem.Globalization.Native.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libSystem.IO.Compression.Native.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libSystem.Security.Cryptography.Native.Android.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libbootstrapperdll.o C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libRuntime.WorkstationGC.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libeventpipe-disabled.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libRuntime.VxsortDisabled.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libstandalonegc-disabled.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libaotminipal.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libbrotlienc.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libbrotlidec.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libbrotlicommon.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libzstd.a --target=x86_64-linux-android21 -g -Wl,--build-id=sha1 -Wl,--as-needed -Wl,-e,0x0 -pthread -ldl -lz -llog -lm -shared -Wl,-z,relro -Wl,-z,now -Wl,--eh-frame-hdr -Wl,-z,max-page-size=16384 --target=x86_64-linux-android24 "-Wl,-soname,libUnnamedProject.so" -Wl,--error-unresolved-symbols -Wl,--no-undefined "C:\a\_work\1\s\bin\Release\dotnet\packs\Microsoft.Android.Runtime.NativeAOT.36.android-x64\36.1.99-ci.dev-grendel-naot-link-api-level.147\runtimes\android-x64\native\libnaot-android.release-static-release.a" "C:\Android\android-sdk\ndk\29.0.14206865\toolchains/llvm/prebuilt/windows-x86_64/sysroot/usr/lib/x86_64-linux-android/libc++_static.a" "C:\Android\android-sdk\ndk\29.0.14206865\toolchains/llvm/prebuilt/windows-x86_64/sysroot/usr/lib/x86_64-linux-android/libc++abi.a" obj\Release\android-x64\android\jni_init_funcs.x86_64.o obj\Release\android-x64\android\environment.x86_64.o -Wl,--discard-all -Wl,--gc-sections" exited with code 1. [C:\a\_work\1\a\TestRelease\02-13_14.27.07\temp\BuildApplicationAndCleanTrueapkNativeAOT\UnnamedProject.csproj]

[grendello]

There are some errors building NativeAOT projects like:

gcc : error : unrecognized command-line option '--target=x86_64-linux-android21' [C:\a\_work\1\a\TestRelease\02-13_14.27.07\temp\BuildApplicationAndCleanTrueapkNativeAOT\UnnamedProject.csproj]
         gcc : error : unrecognized command-line option '--target=x86_64-linux-android24' [C:\a\_work\1\a\TestRelease\02-13_14.27.07\temp\BuildApplicationAndCleanTrueapkNativeAOT\UnnamedProject.csproj]
         C:\Users\cloudtest\.nuget\packages\microsoft.dotnet.ilcompiler\11.0.0-preview.1.26076.102\build\Microsoft.NETCore.Native.targets(391,5): error MSB3073: The command ""gcc" "obj\Release\android-x64\native\UnnamedProject.o" -o "bin\Release\android-x64\native\UnnamedProject.so" -Wl,--version-script="obj\Release\android-x64\native\UnnamedProject.exports" -Wl,--export-dynamic -gz=zlib -fuse-ld=lld C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libSystem.Native.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libSystem.Globalization.Native.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libSystem.IO.Compression.Native.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libSystem.Security.Cryptography.Native.Android.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libbootstrapperdll.o C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libRuntime.WorkstationGC.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libeventpipe-disabled.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libRuntime.VxsortDisabled.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libstandalonegc-disabled.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libaotminipal.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libbrotlienc.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libbrotlidec.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libbrotlicommon.a C:\Users\cloudtest\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.android-x64\11.0.0-preview.1.26076.102/runtimes/android-x64/\native\libzstd.a --target=x86_64-linux-android21 -g -Wl,--build-id=sha1 -Wl,--as-needed -Wl,-e,0x0 -pthread -ldl -lz -llog -lm -shared -Wl,-z,relro -Wl,-z,now -Wl,--eh-frame-hdr -Wl,-z,max-page-size=16384 --target=x86_64-linux-android24 "-Wl,-soname,libUnnamedProject.so" -Wl,--error-unresolved-symbols -Wl,--no-undefined "C:\a\_work\1\s\bin\Release\dotnet\packs\Microsoft.Android.Runtime.NativeAOT.36.android-x64\36.1.99-ci.dev-grendel-naot-link-api-level.147\runtimes\android-x64\native\libnaot-android.release-static-release.a" "C:\Android\android-sdk\ndk\29.0.14206865\toolchains/llvm/prebuilt/windows-x86_64/sysroot/usr/lib/x86_64-linux-android/libc++_static.a" "C:\Android\android-sdk\ndk\29.0.14206865\toolchains/llvm/prebuilt/windows-x86_64/sysroot/usr/lib/x86_64-linux-android/libc++abi.a" obj\Release\android-x64\android\jni_init_funcs.x86_64.o obj\Release\android-x64\android\environment.x86_64.o -Wl,--discard-all -Wl,--gc-sections" exited with code 1. [C:\a\_work\1\a\TestRelease\02-13_14.27.07\temp\BuildApplicationAndCleanTrueapkNativeAOT\UnnamedProject.csproj]

This is odd, it works fine locally. I'll investigate.

[grendello]

So the reason for NAOT tests failing on Windows was that the <Exec> task is confused by the mixture of Unix and Windows path separator chars in $(_NdkBinDir):

SetupOSSpecificProps:
         where /Q "C:\Android\android-sdk\ndk\29.0.14206865\toolchains/llvm/prebuilt/windows-x86_64/bin/clang++"
     1>EXEC : error : Invalid pattern is specified in "path:pattern". [C:\a\_work\1\a\TestRelease\02-13_14.27.07\temp\BindingCustomJavaApplicationClassNativeAOT\App\UnnamedProject.csproj]
         The command "where /Q "C:\Android\android-sdk\ndk\29.0.14206865\toolchains/llvm/prebuilt/windows-x86_64/bin/clang++"" exited with code 2.
         where /Q "gcc"
         "gcc" -fuse-ld=lld -Wl,--version