get the PPC stub temporary label from the mangler instead of

get the PPC stub temporary label from the mangler instead of
using horrible string hacking.  This gives us a different label,
but it's just an assembler temporary, so the name doesn't matter.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75733 91177308-0d34-0410-b5e6-96231b3b80d8