get_build_var and get_abs_build_var are now scripts am: 5a62e765 am: 1722070b

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/3101802



Change-Id: Ic2ef363e588e417284bb8630f439e1131260d5df
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>