Fix option parsing in the gold plugin.

This was broken when options were moved up in r191680. No test because this is
specific LLVMgold.so/libLTO.so.

Patch by Tom Roeder!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191829 91177308-0d34-0410-b5e6-96231b3b80d8