Fix llvm-nm to mach OS X's nm on some tests.

There is still a long way to go for llvm-nm, but at least we now match
nm's letter output in the cases we test for.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193912 91177308-0d34-0410-b5e6-96231b3b80d8