Do not build a separate x86_64h Haswell slice for the iOS simulator.

r199996 added new x86_64h slices for all the Darwin compiler_rt libraries
that had an x86_64 slice, but that is overkill for the iOS Simulator
platform where the x86_64h slice is never used.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@221610 91177308-0d34-0410-b5e6-96231b3b80d8