Add BUILD_BROKEN_ENG_DEBUG_TAGS to soong.log

And add a helper script that can help parse the output from
build_test.bash

Test: check for BUILD_BROKEN_ENG_DEBUG_TAGS in soong.log
Test: go run ../build/soong/scripts/build_broken_logs.go *
Change-Id: Idd0fc8b59770dcdbe44eeba262558708a9497f96