Use the simpler version of sys::fs::remove when possible.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198958 91177308-0d34-0410-b5e6-96231b3b80d8
All backends use MC now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198959 91177308-0d34-0410-b5e6-96231b3b80d8