Disable cfi directives for now, darwin does't support them.

Disable cfi directives for now, darwin does't support them.
These should probably be something like:

  CFI(".cfi_def_cfa_offset 16\n")

where CFI is defined to a noop on darwin and other platforms
that don't support those directives.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44803 91177308-0d34-0410-b5e6-96231b3b80d8