Use filegroups for test-{base,mock,runner} srcs

This allows soong to infer the package of the given srcs, which in turns
make it able to filter the inputs to metalava to exclude unwanted
packages.

This is part of a larger topic of changes intended to remove undesired
classes from the public documentation.

Bug: 187386774
Test: m
Change-Id: I8196c306b743ce6ca8a6452d212f3d7c0b5b2b82
diff --git a/test-mock/Android.bp b/test-mock/Android.bp
index b83bce6..107292c 100644
--- a/test-mock/Android.bp
+++ b/test-mock/Android.bp
@@ -29,7 +29,7 @@
     name: "android.test.mock",
 
     srcs: [
-        "src/**/*.java",
+        ":android-test-mock-sources",
         // Note: Below are NOT APIs of this library. We only take APIs under
         // the android.test.mock package. They however provide private APIs that
         // android.test.mock APIs references to.
@@ -61,3 +61,9 @@
         "api/current.txt",
     ],
 }
+
+filegroup {
+    name: "android-test-mock-sources",
+    srcs: ["src/**/*.java"],
+    path: "src",
+}