Re-commit r294826 and r294781, with a fix on the cmake file to only

compile on powerpc64le.

I cannot locally reproduce this test failure:
http://lab.llvm.org:8011/builders/sanitizer-ppc64le-linux/builds/1363/steps/test%20standalone%20compiler-rt/logs/stdio

Let's see how the buildbot goes.

Differential Revision: https://reviews.llvm.org/D29742

llvm-svn: 295017