The json files used to generate the Android.bp files have more flags
than those specified in the BUILD.gn and *.gni configuration files. This
change ignores the ones added by the build toolchain and keeps only
those added by the webrtc authors.
Bug: 269761242
Test: run cuttlefish in x64, build for arm64 and riscv64
Change-Id: I55f2bdea229cf11c21b5780b2639abb6dd7c3268