[TrimmableTypeMap] Generate the typemap before the NativeAOT inner build so the IDE Compile→Sign flow works

[simonrozsival]

Summary

The NativeAOT trimmable typemap (the generated Java ↔ .NET type map) is consumed by the inner per-RID ILC build — via _AddTrimmableTypeMapAssembliesToIlc → _ReadGeneratedTrimmableTypeMapAssemblies — which reads the generated assembly list at obj/.../typemap/typemap-assemblies.txt. The inner build cannot generate that list: _GenerateTrimmableTypeMap is gated to the outer build ('$(_OuterIntermediateOutputPath)' == '').

_GenerateTrimmableTypeMap's only trigger is AfterTargets="CoreCompile". That hook does not fire when compilation is already up-to-date — which is exactly what happens in the IDE's split build, where Visual Studio (BuildingInsideVisualStudio=true) runs Compile and SignAndroidPackage as two separate MSBuild invocations. During the SignAndroidPackage call the C# is already compiled, so CoreCompile is skipped, the typemap is never generated, and the inner ILC build fails with:

Trimmable typemap assembly list '.../typemap/typemap-assemblies.txt' was not found

A regular command-line Build works because all targets run in one continuous invocation; only the IDE Compile→Sign sequence hits this. Reproduced by the DesignTimeBuildSignAndroidPackage(NativeAOT) test.

Fixes #11775.

Fix

Add a target that forces the typemap to be generated in the outer build before _ResolveAssemblies spawns the inner per-RID ILC build:

<Target Name="_EnsureTrimmableTypeMapGeneratedForNativeAotInnerBuild"
    Condition=" '$(RuntimeIdentifier)' == '' "
    BeforeTargets="_ResolveAssemblies"
    DependsOnTargets="_GenerateTrimmableTypeMap" />

Instead of relying on the fragile AfterTargets="CoreCompile" hook, generation is anchored to _ResolveAssemblies, which always runs before the inner build and runs after compilation (it consumes @(IntermediateAssembly)), so the generator still observes the compiled app assembly. This mirrors the CoreCLR _AddTrimmableTypeMapToLinker target, which forces generation before the (outer) ILLink.

Risk

Low and well-scoped: the new target is conditioned to the outer build (RuntimeIdentifier == '') and lives in the NativeAOT trimmable targets file; it only ensures an already-required step has run. No effect on CoreCLR, managed, or MonoVM paths.

Testing

Verified locally: DesignTimeBuildSignAndroidPackage(NativeAOT) now passes (was failing); DesignTimeBuildSignAndroidPackage(CoreCLR) continues to pass.

Sliced out of #11617 for focused review.

[Copilot]

Pull request overview

This PR fixes a NativeAOT + trimmable typemap build-order problem that occurs in the IDE “Compile → SignAndroidPackage” split invocation flow. It ensures the outer build generates the typemap (and its typemap-assemblies.txt list) before _ResolveAssemblies spawns the inner per-RID NativeAOT/ILC build that consumes that list, preventing inner-build failures when CoreCompile is skipped as up-to-date.

Changes:

• Add an outer-build-only target that runs _GenerateTrimmableTypeMap before _ResolveAssemblies for NativeAOT builds, ensuring the typemap assembly list exists for the inner build.

Show a summary per file

File	Description
src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.Trimmable.NativeAOT.targets	Adds _EnsureTrimmableTypeMapGeneratedForNativeAotInnerBuild to force typemap generation in the outer build prior to _ResolveAssemblies spawning the inner per-RID build.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 0

[simonrozsival]

/review