[One .NET] AOT support

Helpful reading:

* https://github.com/dotnet/runtime/blob/15dec9a2aa5a4236d6ba70de2e9c146867b9d2e0/src/tasks/AotCompilerTask/MonoAOTCompiler.cs
* https://github.com/dotnet/runtime/blob/15dec9a2aa5a4236d6ba70de2e9c146867b9d2e0/src/mono/netcore/nuget/Microsoft.NET.Runtime.MonoAOTCompiler.Task/README.md

To make this work, I moved the existing `<Aot/>` MSBuild task calls to
a new `_AndroidAot` MSBuild target in `Xamarin.Android.Legacy.targets`.

In the .NET 6 targets, there is a *different* `_AndroidAot` MSBuild
target that runs the new `<MonoAOTCompiler/>` MSBuild task. The
`_AndroidAot` target runs per `$(RuntimeIdentifier)` after the linker
completes. Native libraries are added to the
`@(ResolvedFileToPublish)` item group to be included in the final
`.apk`.

To follow convention with Blazor WASM:

https://devblogs.microsoft.com/aspnet/asp-net-core-updates-in-net-6-preview-4/#blazor-webassembly-ahead-of-time-aot-compilation

The `$(RunAOTCompilation)` MSBuild property enables AOT. To help with
backwards compatibility with "legacy" Xamarin.Android, I kept the
`$(AotAssemblies)` MSBuild property intact.

Documentation/guides/OneDotNet.md

@@ -190,6 +190,18 @@ It is recommended to migrate to the new linker settings, as
 [linker]: https://docs.microsoft.com/dotnet/core/deploying/trimming-options
 [linker-full]: https://docs.microsoft.com/dotnet/core/deploying/trimming-options#trimmed-assemblies
 
+## AOT
+
+`$(RunAOTCompilation)` will be the new MSBuild property for enabling
+AOT. This is the same property used for [Blazor WASM][blazor].
+`$(AotAssemblies)` will also enable AOT, in order to help with
+migration from "legacy" Xamarin.Android to .NET 6.
+
+It is recommended to migrate to the new `$(RunAOTCompilation)`
+property, as `$(AotAssemblies)` will eventually be deprecated.
+
+[blazor]: https://devblogs.microsoft.com/aspnet/asp-net-core-updates-in-net-6-preview-4/#blazor-webassembly-ahead-of-time-aot-compilation
+
 ## dotnet cli
 
 There are currently a few "verbs" we are aiming to get working in

build-tools/automation/azure-pipelines.yaml

@@ -49,7 +49,7 @@ variables:
   # - This is a non-fork branch with name containing "mono-" (for Mono bumps)
   IsMonoBranch: $[and(ne(variables['System.PullRequest.IsFork'], 'True'), or(contains(variables['Build.SourceBranchName'], 'mono-'), contains(variables['System.PullRequest.SourceBranch'], 'mono-')))]
   RunAllTests: $[or(eq(variables['XA.RunAllTests'], true), eq(variables['IsMonoBranch'], true))]
-  DotNetNUnitCategories: '& TestCategory != DotNetIgnore & TestCategory != AOT & TestCategory != MkBundle & TestCategory != MonoSymbolicate & TestCategory != PackagesConfig & TestCategory != StaticProject & TestCategory != Debugger & TestCategory != SystemApplication'
+  DotNetNUnitCategories: '& TestCategory != DotNetIgnore & TestCategory != MkBundle & TestCategory != MonoSymbolicate & TestCategory != PackagesConfig & TestCategory != StaticProject & TestCategory != Debugger & TestCategory != SystemApplication'
   NUnit.NumberOfTestWorkers: 4
   GitHub.Token: $(github--pat--vs-mobiletools-engineering-service2)
   CONVERT_JAVADOC_TO_XMLDOC: $[ne(variables['Build.DefinitionName'], 'Xamarin.Android-PR')]
@@ -811,6 +811,17 @@ stages:
         artifactFolder: net6-Interpreter
         useDotNet: true
 
+    - template: yaml-templates/apk-instrumentation.yaml
+      parameters:
+        configuration: $(XA.Build.Configuration)
+        testName: Mono.Android.NET_Tests-Aot
+        project: tests/Mono.Android-Tests/Runtime-Microsoft.Android.Sdk/Mono.Android.NET-Tests.csproj
+        testResultsFiles: TestResult-Mono.Android.NET_Tests-$(XA.Build.Configuration)-Aot.xml
+        extraBuildArgs: /p:RunAOTCompilation=true
+        artifactSource: bin/Test$(XA.Build.Configuration)/net6.0-android/Mono.Android.NET_Tests-Signed.apk
+        artifactFolder: net6-aot
+        useDotNet: true
+
     - task: MSBuild@1
       displayName: shut down emulator
       inputs:

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.After.targets

@@ -18,6 +18,7 @@ This file is imported *after* the Microsoft.NET.Sdk/Sdk.targets.
   <Import Project="..\tools\Xamarin.Android.Bindings.Core.targets" />
   <Import Project="..\tools\Xamarin.Android.Bindings.ClassParse.targets" />
   <Import Project="Microsoft.Android.Sdk.AndroidLibraries.targets" />
+  <Import Project="Microsoft.Android.Sdk.Aot.targets"         Condition=" '$(AndroidApplication)' == 'true' " />
   <Import Project="Microsoft.Android.Sdk.Application.targets" Condition=" '$(AndroidApplication)' == 'true' " />
   <Import Project="Microsoft.Android.Sdk.AssemblyResolution.targets" />
   <Import Project="Microsoft.Android.Sdk.ILLink.targets" />

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.Aot.targets

@@ -0,0 +1,72 @@
+<!--
+***********************************************************************************************
+Microsoft.Android.Sdk.Aot.targets
+
+.NET 6 AOT support. You can find "legacy" Xamarin.Android AOT support
+in Xamarin.Android.Legacy.targets.
+
+For <MonoAOTCompiler/> usage, see:
+* https://github.com/dotnet/runtime/blob/15dec9a2aa5a4236d6ba70de2e9c146867b9d2e0/src/tasks/AotCompilerTask/MonoAOTCompiler.cs
+* https://github.com/dotnet/runtime/blob/15dec9a2aa5a4236d6ba70de2e9c146867b9d2e0/src/mono/netcore/nuget/Microsoft.NET.Runtime.MonoAOTCompiler.Task/README.md
+
+These targets are running within the _ComputeFilesToPublishForRuntimeIdentifiers target.
+They run in a context of an inner build with a single $(RuntimeIdentifier).
+
+***********************************************************************************************
+-->
+<Project>
+
+  <UsingTask TaskName="Xamarin.Android.Tasks.GetAotArguments" AssemblyFile="$(_XamarinAndroidBuildTasksAssembly)" />
+
+  <Target Name="_AndroidAotInputs">
+    <ItemGroup>
+      <_AndroidAotInputs Include="@(ResolvedFileToPublish)" Condition=" '%(Extension)' == '.dll' " />
+    </ItemGroup>
+  </Target>
+
+  <Target Name="_AndroidAot"
+      Condition=" '$(AotAssemblies)' == 'true' and '$(RuntimeIdentifier)' != '' "
+      DependsOnTargets="_AndroidAotInputs"
+      Inputs="@(_AndroidAotInputs)"
+      Outputs="$(_AndroidStampDirectory)_AndroidAot.stamp">
+    <GetAotArguments
+        AndroidAotMode="$(AndroidAotMode)"
+        AndroidNdkDirectory="$(_AndroidNdkDirectory)"
+        AndroidBinUtilsDirectory="$(AndroidBinUtilsDirectory)"
+        AndroidApiLevel="$(_AndroidApiLevel)"
+        ManifestFile="$(_OuterIntermediateOutputPath)android\AndroidManifest.xml"
+        AndroidSequencePointsMode="$(_SequencePointsMode)"
+        AotAdditionalArguments="$(AndroidAotAdditionalArguments)"
+        AotOutputDirectory="$(_AndroidAotBinDirectory)"
+        RuntimeIdentifier="$(RuntimeIdentifier)"
+        EnableLLVM="$(EnableLLVM)"
+        Profiles="@(_AotProfiles)">
+      <Output PropertyName="_AotArguments" TaskParameter="Arguments" />
+    </GetAotArguments>
+    <ItemGroup>
+      <_MonoAOTAssemblies Include="@(_AndroidAotInputs->'%(FullPath)')" AotArguments="$(_AotArguments)" />
+    </ItemGroup>
+    <MakeDir Directories="$(IntermediateOutputPath)aot\" />
+    <MonoAOTCompiler
+        Assemblies="@(_MonoAOTAssemblies)"
+        CompilerBinaryPath="@(MonoAotCrossCompiler->WithMetadataValue('RuntimeIdentifier', '$(RuntimeIdentifier)'))"
+        DisableParallelAot="$(_DisableParallelAot)"
+        LibraryFormat="So"
+        LLVMPath="$(_LLVMPath)"
+        Mode="$(AndroidAotMode)"
+        OutputDir="$(IntermediateOutputPath)aot\"
+        OutputType="Library"
+        UseAotDataFile="false"
+        UseLLVM="$(EnableLLVM)">
+      <Output TaskParameter="CompiledAssemblies" ItemName="_AotCompiledAssemblies" />
+      <Output TaskParameter="FileWrites"         ItemName="FileWrites" />
+    </MonoAOTCompiler>
+    <Touch Files="$(_AndroidStampDirectory)_AndroidAot.stamp" AlwaysCreate="true" />
+    <ItemGroup>
+      <ResolvedFileToPublish
+          Include="@(_AotCompiledAssemblies->'%(LibraryFile)')"
+          ArchiveFileName="libaot-$([System.IO.Path]::GetFileName('%(_AotCompiledAssemblies.LibraryFile)'))"
+      />
+    </ItemGroup>
+  </Target>
+</Project>

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.AssemblyResolution.targets

@@ -31,7 +31,7 @@ _ResolveAssemblies MSBuild target.
   </PropertyGroup>
 
   <Target Name="_ComputeFilesToPublishForRuntimeIdentifiers"
-      DependsOnTargets="_FixupIntermediateAssembly;ResolveReferences;ComputeFilesToPublish"
+      DependsOnTargets="_FixupIntermediateAssembly;ResolveReferences;ComputeFilesToPublish;_AndroidAot"
       Returns="@(ResolvedFileToPublish)">
       <ItemGroup>
         <ResolvedFileToPublish

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.DefaultProperties.targets

@@ -62,6 +62,9 @@
     <AndroidManifest Condition=" '$(AndroidManifest)' == '' and Exists ('Properties\AndroidManifest.xml') and !Exists ('AndroidManifest.xml') ">Properties\AndroidManifest.xml</AndroidManifest>
     <AndroidManifest Condition=" '$(AndroidManifest)' == '' ">AndroidManifest.xml</AndroidManifest>
     <GenerateApplicationManifest Condition=" '$(GenerateApplicationManifest)' == '' ">true</GenerateApplicationManifest>
+    <RunAOTCompilation Condition=" '$(RunAOTCompilation)' == '' and '$(AotAssemblies)' == 'true' ">true</RunAOTCompilation>
+    <RunAOTCompilation Condition=" '$(RunAOTCompilation)' == '' ">false</RunAOTCompilation>
+    <AotAssemblies>$(RunAOTCompilation)</AotAssemblies>
 
     <!--
       Runtime libraries feature switches defaults