[Bug libgomp/64635] darwin produces libgomp-plugin-host_nonshm.1.dylib but tries to load libgomp-plugin-host_nonshm.so.1

[howarth at bromo dot med.uc.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64635

--- Comment #5 from howarth at bromo dot med.uc.edu ---
Created attachment 34469
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34469&action=edit
proposed fix for plugin suffix

Bootstrap and libgomp regression tested on x86_64-apple-darwin14.