[trimmer] pass --disable-opt unusedtypechecks (#9435)

Fixes: #9399

An alternative to: #9411

The .NET trimmer will inline cast statements such as:

	var d = Application.Context.Resources.GetDrawable (resId);
	Assert.IsNotNull (d as NinePatchDrawable);

If `NinePatchDrawable` is not "instantiated" anywhere via `new()`,
then the above statements are rewritten/inlined to:

	var d = Application.Context.Resources.GetDrawable (resId);
	Assert.IsNotNull (null); // BOOM!

We can solve this by passing `--disable-opt unusedtypechecks`, with
`$(_AndroidEnableUnusedTypeChecks)` as a private MSBuild property to
opt out if needed.

Since Java can create these objects, this feels like the reasonable
fix for .NET 9 GA.

I also fixed the `$(RuntimeIdentifiers)` in `TestApks.targets` to
check if someone passed `-r android-arm64`, for example.

Author: jonathanpeppers

build-tools/scripts/TestApks.targets

@@ -18,7 +18,7 @@
 
   <PropertyGroup>
     <!-- APK tests might run on 32-bit emulators -->
-    <RuntimeIdentifiers>android-arm64;android-x86;android-x64;</RuntimeIdentifiers>
+    <RuntimeIdentifiers Condition=" '$(RuntimeIdentifier)' == '' ">android-arm64;android-x86;android-x64;</RuntimeIdentifiers>
     <TestAvdApiLevel Condition=" '$(TestAvdApiLevel)' == '' ">29</TestAvdApiLevel>
     <TestAvdAbi Condition=" '$(TestAvdAbi)' == '' and '$(HostOS)' == 'Darwin' and  '$(HostOSArchitecture)' == 'Arm64' ">arm64-v8a</TestAvdAbi>
     <TestAvdAbi Condition=" '$(TestAvdAbi)' == '' ">x86_64</TestAvdAbi>

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

@@ -16,6 +16,7 @@ This file contains the .NET 5-specific targets to customize ILLink
     <PropertyGroup>
       <TrimmerRemoveSymbols Condition=" '$(AndroidIncludeDebugSymbols)' != 'true' ">true</TrimmerRemoveSymbols>
       <_ExtraTrimmerArgs Condition=" '$(_EnableSerializationDiscovery)' != 'false' ">--enable-serialization-discovery $(_ExtraTrimmerArgs)</_ExtraTrimmerArgs>
+      <_ExtraTrimmerArgs Condition=" '$(_AndroidEnableUnusedTypeChecks)' != 'true' ">--disable-opt unusedtypechecks $(_ExtraTrimmerArgs)</_ExtraTrimmerArgs>
       <!--
         Used for the <ILLink DumpDependencies="$(_TrimmerDumpDependencies)" /> value:
         https://github.com/dotnet/sdk/blob/a5393731b5b7b225692fff121f747fbbc9e8b140/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.ILLink.targets#L150

tests/Mono.Android-Tests/Android.Graphics/NinePatchTests.cs

@@ -25,7 +25,6 @@ public class NinePatchTests
 		};
 
 		[Test, TestCaseSource (nameof (NinePatchDrawables))]
-		[DynamicDependency (DynamicallyAccessedMemberTypes.All, typeof (NinePatchDrawable))]
 		public void DrawableFromRes_ShouldBeTypeNinePatchDrawable (int resId, string name)
 		{
 			var d = Application.Context.Resources.GetDrawable (resId);
@@ -34,7 +33,6 @@ public void DrawableFromRes_ShouldBeTypeNinePatchDrawable (int resId, string nam
 		}
 
 		[Test, TestCaseSource (nameof (NinePatchDrawables))]
-		[DynamicDependency (DynamicallyAccessedMemberTypes.All, typeof (NinePatchDrawable))]
 		public void DrawableFromResStream_ShouldBeTypeNinePatchDrawable (int resId, string name)
 		{
 			var value = new Android.Util.TypedValue ();