Revert premature instructions to build __sync_fetch_*

My commits got a bit twisted when I was working on both embedded support and
__sync stuff on the same branch. Sorry about that.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@194886 91177308-0d34-0410-b5e6-96231b3b80d8