[compiler-rt] r253483 - [PGO] Runtime support for value profiling.


I'm currently bisecting a buildbot regression in the clang-cmake-mips builder and I've ended up with a range of commits, all of them are either this commit or one of its corrections. The commits are r253483, r253489, r253492, and r253496. I'm going to try reverting these in my working copy and if that works I'll commit the revert.

The first build to fail is http://lab.llvm.org:8011/builders/clang-cmake-mips/builds/10816 and the first one to show the current failures is http://lab.llvm.org:8011/builders/clang-cmake-mips/builds/10819.