When outputing a non-lazy pointer for a stub, we may need to fill in the value

When outputing a non-lazy pointer for a stub, we may need to fill in the value
for the NLP because the object it's pointing to may be internal to the file.

This seems counter-intuitive, but bear with me. When we place the LSDA into the
TEXT section, the type info pointers need to be indirect and pc-rel. We
accomplish this by using NLPs. However, sometimes the types are local to the
file. GCC gets around this by not using a NLP in this case, but a "regular"
indirection like this:

GCC_except_tbl:
  .long Lfoo-.

__ZTIA:  @ This is local
  ...

Lfoo:
  .long __ZTIA

LLVM prefers NLPs on Darwin. In fact, it's more optimal for load performance to
use them.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98218 91177308-0d34-0410-b5e6-96231b3b80d8