Separate creation of signature patterns from overlap checking am: 67b9d61a...

Separate creation of signature patterns from overlap checking am: 67b9d61a am: 0623c3e8 am: b32b624d am: 475968b5

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/1788091

Change-Id: I4726bd873538233660babaa7c831c8b1536edeca