Implement experimental build type

Summary:
Currently only sets using our local 3.4 llvm toolchain (https://github.com/codefireXperiment/prebuilts_clang_linux-x86_3.4)
as the default CC.

Test plan: fix up all C99/Clang violations project wide

Reviewers: randall.rushing, synergy

Reviewed By: synergy

Differential Revision: http://review.codefirex.com/D547

Change-Id: Ibf94c1edae126aedde2174b785a8d01f4beb38cd