This only matters if you pull clang for building the packager.
clang binaries gets pulled in to third_party/llvm-build if you run
the script in tools/clang/scripts/update.sh.
clang is useful for ASAN and style (and better compiler error output).
Change-Id: Id615d739f80e92036fe13c3152569e51aed8a7f0
Rintaro Kuroiwa
Kongqun Yang