This fixes a few issues with pe/coff build-ids that were discovered since the

This fixes a few issues with pe/coff build-ids that were discovered since the
original patches were posted:

  pe/coff: Display GUID build-id in the conventional way
  pe/coff: Don't interpret debug directory in section with no contents
  pe/coff: Keep .build-id with --only-keep-debug
  pe/coff: Don't break .build-id with objcopy/strip

	* peXXigen.c (pe_print_debugdata): Don't interpret debug directory
	in a section with no contents.
	(is_vma_in_section, find_section_by_vma): New functions.
	(_bfd_XX_bfd_copy_private_bfd_data_common): Recalculate file
	offsets in the debug directory.
	(_bfd_XXi_slurp_codeview_record, _bfd_XXi_write_codeview_record):
	Byte-swap GUID from little-endian to big-endian order for
	consistent and conventional display.

	* objcopy.c (is_nondebug_keep_contents_section): New function.
	(setup_section): Use it.