[DWARF] Put linkage-name on abstract origin even when there's a declaration.

In r266692, we made it possible to emit linkage names for just inlined
functions, putting the attribute on the abstract origin. Make sure we
don't think the linkage-name was already emitted on a declaration.

Differential Revision: http://reviews.llvm.org/D27320

llvm-svn: 288450
2 files changed