Merge "Revert^3 "Prevent unspecified values in soong_config_string_variable"" am: dee36f45

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/2058887



Change-Id: I4b49b2c4b536f40927dd5c3cddc86e12509b2ea2
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>