Add filegroup_test.go to sources

I don't think it was running before.

Test: yes
Change-Id: Ia3bf53ddcc1ddefd7a236122256594ba764ee8e5
(cherry picked from https://android-review.googlesource.com/q/commit:7a444cec60ec4e70d6c8581ef45c7f0c3c1927f5)
Merged-In: Ia3bf53ddcc1ddefd7a236122256594ba764ee8e5
diff --git a/android/Android.bp b/android/Android.bp
index 65332b2..c0a35ac 100644
--- a/android/Android.bp
+++ b/android/Android.bp
@@ -106,6 +106,7 @@
         "depset_test.go",
         "deptag_test.go",
         "expand_test.go",
+        "filegroup_test.go",
         "fixture_test.go",
         "gen_notice_test.go",
         "license_kind_test.go",