Don't create .eh_frame_hdr on shared lib bfd

Don't create .eh_frame_hdr on shared lib bfd

If no object files have .eh_frame, but some shared library does, then
ld creates a .eh_frame_hdr section using the shared library bfd.  This
is silly since shared library .eh_frame sections don't contribute to
the output .eh_frame and thus no .eh_frame_hdr is needed.

Also, the bfd section list and count is cleared for shared libraries,
and a zero section count used as a flag in lang_check to omit a call
to bfd_merge_private_bfd_data for shared libraries.  If we create a
section on a shared lib bfd then ld will wrongly attempt to merge the
shared library private bfd data.

	PR 17742
	* ld/emultempl/elf32.em (gld${EMULATION_NAME}_after_open): Exclude
	shared libraries in loop looking for .eh_frame sections.
	Similarly for build-id loop.