Merge "Generate build_number.txt only once" into main am: b7dbc854 am:...

Merge "Generate build_number.txt only once" into main am: b7dbc854 am: 28603782 am: ef3ed750 am: 4b82b156

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/2768665



Change-Id: Ie6deed2fee5555e24c56f880adf2030a07cd9b32
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>