Add test for manifest merger

Add a test for the manifest merger command line that would have prevented
b/291252863.

Bug: 291252863
Test: TestManifestMerger
Change-Id: I8c025efe7ccb06ad97b405e2927a4df07f9d3f27
diff --git a/java/Android.bp b/java/Android.bp
index e079869..4450c42 100644
--- a/java/Android.bp
+++ b/java/Android.bp
@@ -80,6 +80,7 @@
     ],
     testSrcs: [
         "aar_test.go",
+        "android_manifest_test.go",
         "androidmk_test.go",
         "app_import_test.go",
         "app_set_test.go",