a patch to set ELF header flags for empty linker output files

[Jim Wilson]

After considering the comments I've seen, I've decided that HJ's approach of
ignoring empty (bfd->sections == NULL) object files is the better solution.

So now the only question in my mind is whether we fix this just in the
elfxx-ia64.c file similar to what was already done in the elf32-arm.h
file, or whether we try to fix it for all targets with HJ's ldlang.c
patch.  I can make the elfxx-ia64.c change on my own, but can't make the
ldlang.c change unless others agree that it is a good idea.

Jim