Add utility function find-files-in-subdirs

find-files-in-subdirs uses utility find to find given files in the given
subdirs. This function uses $(1), instead of LOCAL_PATH as the base.

Change-Id: Ib76631c97acd257d651a580cbad767606874f5d0
Merge "Add utility function find-files-in-subdirs"
Merge remote-tracking branch 'aosp/master' into kk44
Update from AOSP