[jonathanpeppers]

Stacked on #13322. Reuse its MonoAndroidHelper.RunProcess(TaskEnvironment, …) overload for the aapt2 version probe.

ResolveAndroidTooling still requires process-wide working-directory and environment handling under -mt. Use MultithreadedAndroidTask and declare [MSBuildMultiThreadableTask] so it can run in-process with other tasks.

Resolve SDK and tool paths through TaskEnvironment, use project-specific PATHEXT, and start aapt2 with the project environment. Keep the existing tool search order and diagnostics. Extend the existing cache test to cover distinct project directories, relative paths, child-process environment and working directory, and cache reuse.

Validated on Windows with a locally built .NET 11 RC2 SDK after rebasing:

• bin\Debug\dotnet\dotnet.exe build Microsoft.Android.slnx -m:4 -nr:false -v:minimal: passed, including the task-authoring analyzer; 0 errors.
• dotnet-local.cmd test bin\TestDebug\net10.0\Xamarin.Android.Build.Tests.dll --filter "(FullyQualifiedName~ResolveSdksTaskTests|FullyQualifiedName~ValidateJavaVersionTests|Name~MigratedTasksHaveDirectAttribute)&Name!~ToolingTargetRejectsOldJavaForModernAndroidApi": passed, 62 tests. The two excluded parent integration cases failed before reaching the tasks with NETSDK1147 (missing Android workload). Local workload setup was attempted; it is blocked by the .NET 11 RC2 SDK lacking the microsoft-net-runtime-mono-tooling-net11 workload referenced by the current manifest.
• bin\Debug\dotnet\dotnet.exe msbuild <validation>\parallel-tooling.proj -m -nr:false -v:minimal: passed. The local harness runs two actual task instances and checks API level, build-tools path, and aapt2 version.
• The same harness with -m -mt -nr:false -warnaserror:MSB4286,MSB4287,MSB4288: passed. binlogtool found no TaskHost fallback or MT safety diagnostics.

Before rebasing, the 7 MultithreadedAndroidTaskTests passed, including file-lock diagnostics. The expanded cache test was also confirmed to fail separately for a wrong child working directory and a missing project environment variable.

Temporary .NET 11 build settings and the local test-only change that prevents teardown from killing shared adb processes were restored before commit. No device tests were needed for this tooling-only change.

[Copilot]

🟡 Changes recommended

The expanded test would still pass with process-wide environment and working-directory values, leaving project-specific child-process execution without regression coverage.

1 open issue

• Add regression coverage for project-specific environment and working directory · New

What changed in this PR

Enables ResolveAndroidTooling to run in-process during multithreaded MSBuild execution by using project-specific paths and environment settings instead of process-wide state.

Changes:

• Migrates the task to MultithreadedAndroidTask with a direct execution attribute.
• Uses TaskEnvironment for tool discovery and aapt2 launches, and runtime platform detection for bundled tool paths.
• Extends cache tests to cover separate project directories, relative paths, and project-specific PATHEXT.

File	Description
src/​Xamarin.Android.Build.Tasks/​Utilities/​MonoAndroidHelper.Nullable.cs	Adds executable lookup using the project environment.
src/​Xamarin.Android.Build.Tasks/​Utilities/​MonoAndroidHelper.cs	Uses runtime platform detection for OS-specific tool paths.
src/​Xamarin.Android.Build.Tasks/​Tests/​Xamarin.Android.Build.Tests/​Tasks/​ResolveSdksTaskTests.cs	Expands project-isolation and cache-reuse coverage.
src/​Xamarin.Android.Build.Tasks/​Tasks/​ResolveAndroidTooling.cs	Enables multithreaded execution and project-scoped path and process handling.

_{Review effort: Balanced}

[jonathanpeppers]

@dalexsoto review