Remove /FS as it's auto-added by CMake 2.8.12.1; also, remove /wd4221 as 4221 is a linker warning, not a compiler warning

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@200564 91177308-0d34-0410-b5e6-96231b3b80d8