Add SystemUI-tests-utils filegroup to reuse in downstream

Because SystemUI-tests android_library conatins AndroidManifest.xml,
it is diffecult to use test utility classes in SystemUITests from
downstream, such as ArcSystemUITests. Having a separate filegroup
module may help to address such difficulty.

Bug: 140464398
Test: make -j SystemUI SystemUITests
Change-Id: Idfc65a3afb30e58efee82a2eccbdbc2b26297364

packages/SystemUI/Android.bp

@@ -76,6 +76,16 @@ android_library {
     plugins: ["dagger2-compiler-2.19"],
 }
 
+filegroup {
+    name: "SystemUI-tests-utils",
+    srcs: [
+        "tests/src/com/android/systemui/statusbar/NotificationEntryBuilder.java",
+        "tests/src/com/android/systemui/statusbar/RankingBuilder.java",
+        "tests/src/com/android/systemui/statusbar/SbnBuilder.java",
+    ],
+    path: "tests/src",
+}
+
 android_library {
     name: "SystemUI-tests",
     manifest: "tests/AndroidManifest.xml",