[PATCH] Add CMake option LLVM_USE_SANITIZER to allow bootstrap of LLVM/Clang under ASan/MSan.

[Alexey Samsonov]

  I've mailed the part which is not connected w/ sanitizers as http://llvm-reviews.chandlerc.com/D535

http://llvm-reviews.chandlerc.com/D459

BRANCH
  svn

ARCANIST PROJECT
  llvm