Normalize reverse-mapped Java source paths

Convert manifest-style JNI paths to the native directory separator at the filesystem copy boundary.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: simonrozsival

src/Xamarin.Android.Build.Tasks/Tasks/GenerateTrimmableTypeMap.cs

@@ -366,6 +366,7 @@ internal ITaskItem [] CopyJavaSourcesFromInputDirectory (IReadOnlyList<Generated
 			if (relativePath == null) {
 				continue;
 			}
+			relativePath = NormalizeJavaSourceRelativePath (relativePath, Path.DirectorySeparatorChar);
 			string inputPath = Path.Combine (JavaSourceInputDirectory ?? "", relativePath);
 			if (!File.Exists (inputPath)) {
 				Log.LogCodedError ("XA4255", Properties.Resources.XA4255, inputPath);
@@ -385,6 +386,9 @@ internal ITaskItem [] CopyJavaSourcesFromInputDirectory (IReadOnlyList<Generated
 		return items.ToArray ();
 	}
 
+	internal static string NormalizeJavaSourceRelativePath (string relativePath, char directorySeparator)
+		=> relativePath.Replace ('/', directorySeparator);
+
 	string? GetOriginalJavaSourceRelativePath (string generatedRelativePath)
 	{
 		if (r8Mapping == null || reverseR8Mapping == null || !generatedRelativePath.EndsWith (".java", StringComparison.OrdinalIgnoreCase)) {

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

@@ -178,6 +178,15 @@ public void CopyJavaSources_ReverseMapsObfuscatedNestedClassPath ()
 			FileAssert.DoesNotExist (Path.Combine (outputDir, "g.java"));
 		}
 
+		[TestCase ('/', "com/example/Outer$Inner.java")]
+		[TestCase ('\\', "com\\example\\Outer$Inner.java")]
+		public void NormalizeJavaSourceRelativePath_UsesDirectorySeparator (char directorySeparator, string expected)
+		{
+			Assert.AreEqual (
+				expected,
+				GenerateTrimmableTypeMap.NormalizeJavaSourceRelativePath ("com/example/Outer$Inner.java", directorySeparator));
+		}
+
 		[TestCase ("C\tcom/example/First\nC\tcom/example/Second\n", TestName = "CopyJavaSources_MergedClassIsAmbiguous")]
 		[TestCase ("C\tcom/example/Unrelated\n", TestName = "CopyJavaSources_MissingRequiredReverseEntry")]
 		public void CopyJavaSources_InvalidReverseMappingUsesXA4327 (string manifest)