Fix some dlx fails

Fix some dlx fails

Generic linker ELF targets using CREATE_OBJECT_SYMBOLS in their
scripts run into a problem.  The file symbols are created by
_bfd_generic_link_output_symbols in each object file, in the section
corresponding to the CREATE_OBJECT_SYMBOLS section, typically .text.
If it so happens that the output .text section is stripped due to
being empty, then elf.c:assign_section_numbers won't assign an ELF
section number and swap_out_syms will report "unable to find
equivalent output section" for the object symbols.  Fix this by
always keeping an output section with CREATE_OBJECT_SYMBOLS.

	* ldlang.c (lang_size_sections_1): Set SEC_KEEP on
	create_object_symbols_section.
	* testsuite/ld-elf/pr22319.d: Don't xfail dlx.