[release/10.0.1xx] Support for exempting native libraries from JNI preload

[jonathanpeppers]

Backport of: #10787
Fixes: #10617
Context: cba39dc

cba39dc introduced support for preloading of JNI native libraries at application startup. However, it appears that in some scenarios this behavior isn't desired.

This PR introduces a mechanism which allows exempting some or all (with exception of the BCL libraries) libraries from the preload mechanism.

In order to not preload any JNI libraries it's now possible to set the $(AndroidIgnoreAllJniPreload) MSBuild property to true.

It is also possible to exempt individual libraries from preload by adding their name to the AndroidNativeLibraryNoJniPreload MSBuild item group, for instance:

<ItemGroup>
  <AndroidNativeLibraryNoJniPreload Include="libMyLibrary.so" />
</ItemGroup>

[Copilot]

Pull request overview

Adds an opt-out mechanism for the JNI native-library preload behavior introduced for .NET Android startup, allowing projects to exempt specific native libraries (or all of them) from being preloaded while still preserving required framework defaults.

Changes:

• Introduces $(AndroidIgnoreAllJniPreload) and @(AndroidNativeLibraryNoJniPreload) to control JNI preload behavior from MSBuild.
• Extends native application config generation to honor “always preload” and “never preload” library lists.
• Adds a small native “test JNI library” plus new build/test infrastructure and NUnit tests validating preload behavior.

Reviewed changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
src/native/native.targets	Builds a new test JNI library as part of native runtime build orchestration.
src/native/common/test-jni-library/stub.cc	Adds a minimal JNI_OnLoad implementation for preload testing.
src/native/common/test-jni-library/CMakeLists.txt	CMake rules to build and place the test JNI library in test output.
src/native/CMakePresets.json.in	Adds XA_TEST_OUTPUT_DIR to CMake cache variables.
src/native/CMakeLists.txt	Requires XA_TEST_OUTPUT_DIR and wires the test JNI library subdirectory.
src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets	Adds MSBuild property + item groups and passes new inputs to config generation.
src/Xamarin.Android.Build.Tasks/Utilities/MonoAndroidHelper.cs	Adds helpers for minimum API lookup and normalizing native library names.
src/Xamarin.Android.Build.Tasks/Utilities/ApplicationConfigNativeAssemblyGeneratorCLR.cs	Implements “ignore/always preload” decision logic for CoreCLR config generation.
src/Xamarin.Android.Build.Tasks/Utilities/ApplicationConfigNativeAssemblyGenerator.cs	Implements the same “ignore/always preload” decision logic for MonoVM config generation.
src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Android/AndroidItem.cs	Adds a ProjectTools item wrapper for AndroidNativeLibraryNoJniPreload.
src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Android/AndroidBuildActions.cs	Adds build action constant for AndroidNativeLibraryNoJniPreload.
src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Utilities/EnvironmentHelper.cs	Adds parsing/validation helpers for JNI preload index data from generated native sources.
src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildTest3.cs	New NUnit coverage for JNI preload inclusion/exclusion scenarios.
src/Xamarin.Android.Build.Tasks/Tasks/GenerateNativeApplicationConfigSources.cs	Wires MSBuild inputs into the native config generator.
build-tools/xaprepare/xaprepare/xaprepare.targets	Adds placeholder replacement for @TestOutputDirectory@.
build-tools/xaprepare/xaprepare/Steps/Step_GenerateFiles.cs	Plumbs XA_TEST_OUTPUT_DIR placeholder into generated CMake presets.
build-tools/xaprepare/xaprepare/Application/Properties.Defaults.cs.in	Adds KnownProperties.TestOutputDirectory default wiring.
build-tools/xaprepare/xaprepare/Application/KnownProperties.cs	Adds TestOutputDirectory to known xaprepare properties.
Documentation/docs-mobile/building-apps/build-properties.md	Documents AndroidIgnoreAllJniPreload.
Documentation/docs-mobile/building-apps/build-items.md	Documents AndroidNativeLibraryNoJniPreload.

[jonathanpeppers]

This has test failures like:

Expected the '.byte' field type in file 'C:\a_work\1\a\TestRelease\03-03_23.16.24\temp\NativeLibraryJniPreloadDefaultsWorkCoreCLR\obj\Release\android\environment.arm64-v8a.s:53': .word. File generated from 'C:\a_work\1\a\TestRelease\03-03_23.16.24\temp\NativeLibraryJniPreloadDefaultsWorkCoreCLR\obj\Release\android\environment.arm64-v8a.ll'
String lengths are both 5. Strings differ at index 1.
Expected: ".byte"
But was:  ".word"
------------^