[Tests] Add NativeAOT regression test for R8-kept runtime ACWs

Adds NativeAotKeepsRuntimeAcwJavaTypesUnderR8, which builds a Release NativeAOT
app with r8 and asserts that classes.dex still contains the runtime
UncaughtExceptionMarshaler ACW kept by the generated NativeAOT ProGuard rules.
If those keep rules are missing, R8 tree-shakes the runtime JCWs and the app
crashes at startup inside JavaInteropRuntime.init.

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

Author: simonrozsival

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildTest2.cs

@@ -1548,6 +1548,36 @@ public void BuildProguardEnabledProject ([Values ("", "android-arm64")] string r
 			}
 		}
 
+		[Test]
+		public void NativeAotKeepsRuntimeAcwJavaTypesUnderR8 ()
+		{
+			const bool isRelease = true;
+			if (IgnoreUnsupportedConfiguration (AndroidRuntime.NativeAOT, release: isRelease)) {
+				return;
+			}
+			var proj = new XamarinAndroidApplicationProject {
+				IsRelease = isRelease,
+				LinkTool = "r8",
+			};
+			proj.SetRuntime (AndroidRuntime.NativeAOT);
+			using (var b = CreateApkBuilder ()) {
+				Assert.IsTrue (b.Build (proj), "Build should have succeeded.");
+
+				var intermediate = Path.Combine (Root, b.ProjectDirectory, proj.IntermediateOutputPath);
+				var dexFile = Path.Combine (intermediate, "android", "bin", "classes.dex");
+				FileAssert.Exists (dexFile);
+
+				// Regression test: the trimmable NativeAOT path generates its ACW keep rules from the
+				// ILC DGML into proguard_project_references.cfg. If that file is not passed to R8, R8
+				// tree-shakes the runtime ACW/JCW classes out of classes.dex and the app crashes at
+				// startup inside JavaInteropRuntime.init with a ClassNotFoundException for the
+				// UncaughtExceptionMarshaler Java Callable Wrapper. The JCW class name is CRC-hashed
+				// (e.g. `scrc64...UncaughtExceptionMarshaler`), so match on the type name suffix.
+				Assert.IsTrue (DexUtils.ContainsClass ("UncaughtExceptionMarshaler;", dexFile, AndroidSdkPath),
+					$"`{dexFile}` should include the UncaughtExceptionMarshaler ACW kept by the generated NativeAOT ProGuard rules.");
+			}
+		}
+
 		XamarinAndroidApplicationProject CreateMultiDexRequiredApplication (string debugConfigurationName = "Debug", string releaseConfigurationName = "Release")
 		{
 			var proj = new XamarinAndroidApplicationProject (debugConfigurationName, releaseConfigurationName);