GCC does not generate `__unix` nor `unix` macros. The latter already
intrudes into the user's namespace and should be avoided. Use the
canonical spelling of `__unix__` across all the targets.
llvm-svn: 294148
This is still a fairly odd test. Clang wants to run gcc for assembling. At
least with -### it only prints that instead of actually trying to run it with
-ccc-echo.
llvm-svn: 186945
Saleem Abdulrasool