Revert "Temporarily revert r220777 to sort out build bot breakage."

This reverts commit r221028. Later commits depend on this and
reverting just this one causes even more bots to fail.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221041 91177308-0d34-0410-b5e6-96231b3b80d8