[msan] Handling of atomic load/store, atomic rmw, cmpxchg.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191287 91177308-0d34-0410-b5e6-96231b3b80d8
Remove error output from configure if CFLAGS is set (r174313).

This fixes PR16724.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191289 91177308-0d34-0410-b5e6-96231b3b80d8