Add support for inline asm symbols in llvm-ar.

This should allow llvm-ar to be used instead of gnu ar + plugin in a LTO
build. I will add a release note about it once I finish a LTO bootstrap with it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212287 91177308-0d34-0410-b5e6-96231b3b80d8