Support recording compilation info

Summary:
Depends on D320. Record non-mergeable compiler optimizations that are in use,
in a .gnu.switches.text section if BUILD_RECORD_COMPILATION_INFO is set.

Test Plan: win

Reviewers: randall.rushing, Mustaavalkosta, michyprima, Roach, synergy

Reviewed By: synergy

Differential Revision: http://review.codefirex.com/D321