[automerged blank] Add filegroup_test.go to sources 2p: dfe8dca369

Blank merge reason: Change-Id Ia3bf53ddcc1ddefd7a236122256594ba764ee8e5 with SHA-1 7a444cec60 is in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/build/soong/+/22069506


Change-Id: I6878057ff954ea3636c1e074a066dcc53c92f7f7
Merged-In: Ia3bf53ddcc1ddefd7a236122256594ba764ee8e5