Merge "Revert "Generate build_number.txt only once"" into main am: eba51bf9...

Merge "Revert "Generate build_number.txt only once"" into main am: eba51bf9 am: 16f28221 am: 09459072

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/2768007



Change-Id: I67d60fbab714a16b250238092ac92ca4cf7a454e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>