ANDROID: build.config.common: Add BUILDTOOLS_PREBUILT_BIN

This was added to build.config.common in all of the other branches but
not this one during the build.config refactor. Without this, it is
possible to get different build results across host environments.

Change-Id: Ie72dd902adfa4b3d8fed8bfbadf13a78cf55f1fa
Fixes: f04f84fd ("ANDROID: refactor build.config files to remove duplication")
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>