Stop producing func.eh symbols on Darwin.

According Nick Kledzik (http://llvm.org/bugs/show_bug.cgi?id=19430#c2):
"... mach-o no longer needs names in the __eh_frame section (and has not for
years)."

Iain Sandoe confirms it is also unnecessary for their old darwin support.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211500 91177308-0d34-0410-b5e6-96231b3b80d8