Fix the new LTOCodeGenerator setup in gold to parse options before using MAttrs.

This fixes a regression that made clang -flto -Wl,--plugin-opt=-mattr=+aes not
pass the "+aes" option to the LTOCodeGenerator attributes.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211804 91177308-0d34-0410-b5e6-96231b3b80d8