Merge "Disallow unknown fields in soong variables file" into main am: 4eef64a7 am: 142cf7a3

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/3114140



Change-Id: I2b5e0f4615f90809a32e1a596dda4c30441dd7d5
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>