Fix CheckNothingIsDeletedByIncrementalClean by moving _RemoveRegisterFlag to stamp directory

The _RemoveRegisterAttribute target's stamp file (shrunk.flag) was located at
$(MonoAndroidIntermediateAssemblyDir)shrunk/shrunk.flag, inside the tree
globbed by <FileWrites Include="$(MonoAndroidIntermediateAssemblyDir)**" />.
Since _RemoveRegisterAttribute runs during SignAndroidPackage (after
IncrementalClean), the glob didn't capture the stamp on build 1 but did on
build 2, causing FileListAbsolute.txt to grow.

Fix by:
- Moving the stamp to $(_AndroidStampDirectory)_RemoveRegisterAttribute.stamp,
  following the existing naming convention for stamp files
- Adding _RemoveRegisterAttribute to IncrementalCleanDependsOn so it runs
  before _AddFilesToFileWrites, ensuring the stamp exists when the
  $(_AndroidStampDirectory)*.stamp glob captures it
- Removing the now-unnecessary MakeDir for the old shrunk directory (it was
  only needed for the flag file, not for shrunk assemblies which go to the
  publish directory)

Author: sbomer

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

@@ -54,6 +54,7 @@ properties that determine build ordering.
     </BuildDependsOn>
     <IncrementalCleanDependsOn>
       _PrepareAssemblies;
+      _RemoveRegisterAttribute;
       _CompileDex;
       $(_AfterCompileDex);
       _AddFilesToFileWrites;

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.LlvmIr.targets

@@ -9,7 +9,7 @@
   <UsingTask TaskName="Xamarin.Android.Tasks.GenerateProguardConfiguration" AssemblyFile="$(_XamarinAndroidBuildTasksAssembly)" />
 
   <PropertyGroup>
-    <_RemoveRegisterFlag>$(MonoAndroidIntermediateAssemblyDir)shrunk\shrunk.flag</_RemoveRegisterFlag>
+    <_RemoveRegisterFlag>$(_AndroidStampDirectory)_RemoveRegisterAttribute.stamp</_RemoveRegisterFlag>
     <!-- Inject typemap-specific targets into build dependency chains -->
     <_BeforeAddStaticResources>$(_BeforeAddStaticResources);_GetMonoPlatformJarPath</_BeforeAddStaticResources>
     <_BeforeCompileJava>$(_BeforeCompileJava);_GetMonoPlatformJarPath</_BeforeCompileJava>
@@ -325,7 +325,6 @@
     <RemoveRegisterAttribute
         Condition=" '$(_AndroidRuntime)' != 'NativeAOT' and '$(PublishReadyToRun)' != 'true' "
         ShrunkFrameworkAssemblies="@(_ShrunkAssemblies)" />
-    <MakeDir Directories="$(MonoAndroidIntermediateAssemblyDir)shrunk" />
     <Touch Files="$(_RemoveRegisterFlag)" AlwaysCreate="true" />
   </Target>
 

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/IncrementalBuildTest.cs

@@ -143,12 +143,12 @@ public void CheckNothingIsDeletedByIncrementalClean ([Values] bool enableMultiDe
 					FileAssert.Exists (file);
 					File.SetLastWriteTimeUtc (file, DateTime.UtcNow);
 				}
-				Assert.IsTrue (b.Build (proj, doNotCleanupOnUpdate: true, saveProject: false), "Second should have succeeded");
-				b.Output.AssertTargetIsNotSkipped ("_CleanMonoAndroidIntermediateDir");
-				var stampFiles = Path.Combine (intermediate, "stamp", "_ResolveLibraryProjectImports.stamp");
-				FileAssert.Exists (stampFiles, $"{stampFiles} should exist!");
-				var libraryProjectImports = Path.Combine (intermediate, "libraryprojectimports.cache");
-				FileAssert.Exists (libraryProjectImports, $"{libraryProjectImports} should exist!");
+			Assert.IsTrue (b.Build (proj, doNotCleanupOnUpdate: true, saveProject: false), "Second should have succeeded");
+			b.Output.AssertTargetIsNotSkipped ("_CleanMonoAndroidIntermediateDir");
+			var stampFiles = Path.Combine (intermediate, "stamp", "_ResolveLibraryProjectImports.stamp");
+			FileAssert.Exists (stampFiles, $"{stampFiles} should exist!");
+			var libraryProjectImports = Path.Combine (intermediate, "libraryprojectimports.cache");
+			FileAssert.Exists (libraryProjectImports, $"{libraryProjectImports} should exist!");
 
 				//No changes
 				Assert.IsTrue (b.Build (proj, doNotCleanupOnUpdate: true, saveProject: false), "Third should have succeeded");

src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets

@@ -1917,7 +1917,6 @@ because xbuild doesn't support framework reference assemblies.
   <CopyIfChanged
     SourceFiles="@(_ResolvedAssemblies->'%(Identity).config')"
     DestinationFiles="@(_ShrunkAssemblies->'%(Identity).config')" />
-  <MakeDir Directories="$(MonoAndroidIntermediateAssemblyDir)shrunk" />
 </Target>
 
 <Target Name="_ResolveSatellitePaths"