Merge "bp2build: Add special arch-variant targets." am: 3bc7a1ba47 am: 1f211a9b88 am: 3796dae3e1

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/1853859

Change-Id: I44106be556298680e18b8877f1b4e30001f5324b