[PATCH] ignore --disable-free in clang when leak detection is enabled

[Reid Kleckner]

  I'd hate to have to a full clean build with a new -D flag just to change
  the sense of this one obscure function.  You guys are the ones pioneering
  this testing, though, so is this really what you want?  :)

http://llvm-reviews.chandlerc.com/D2475