[ELF] - Do not try to create .eh_frame_hdr for relocatable output.

.eh_frame_hdr is a header constructed for .eh_frame sections.
We do not proccess .eh_frame when doing relocatable output,
so should not try to create .eh_frame_hdr too.
Previous behavior without this patch is segfault.

Fixes PR32118.

Differential revision: https://reviews.llvm.org/D30566

llvm-svn: 297365