GOLD/DWP: exit without segfault if the binary is not built with debug fission.

dwp segfaults when trying to get .dwp file from a binary built without
debug fission. This patch fixes that.
upstream thread is

TEST=dwp still works with files built with debug fission and dwp does not
     segfault on files that are not built with debug fission.
1 file changed
tree: 3fc94ba4a94bacfa87f11131c74f6278d5a192a1
  1. binutils-2.25/