dwarf2out: Fix up split-dwarf .debug_macro handling [PR99319]

dwarf2out: Fix up split-dwarf .debug_macro handling [PR99319]

The -gsplit-dwarf changes came a few months after .debug_macro
and the r0-120109 changes just changed the 2nd operand of
DW_MACRO_GNU_{define,undef}_indirect from the usual .debug_str
section offset argument to leb128 index into .debug_str_offsets
without changing the opcodes.

DWARF5 standardized different opcodes for those, but GCC hasn't been changed
yet for that.
This patch starts using DW_MACRO_define_strx and DW_MACRO_undef_strx
instead of DW_MACRO_define_strp and DW_MACRO_undef_strp when -gsplit-dwarf
-gdwarf-5 -g3.  I'm not sure what to do if anything with the -gdwarf-4
-gsplit-dwarf -g3 -gno-strict-dwarf case, we've been emitting it that way
for 8 years and it is an extension, so presumably the consumers that cared
have already hacks to handle DW_MACRO_GNU_{define,undef}_indirect
differently in .debug_macro 4 sections depending on if it is
.debug_macro.dwo or .debug_macro.
Another change the patch does is that it will use
DW_MACRO_{define,undef}_str{p,x} even with -gdwarf-5 -gstrict-dwarf -g3,
for DWARF 4 we were doing that only for -gno-strict-dwarf as we've emitted
.debug_macro section only in that case.

2021-03-02  Jakub Jelinek  <jakub@redhat.com>

	PR debug/99319
	* dwarf2out.c (output_macinfo_op): Use DW_MACRO_*_str* even with
	-gdwarf-5 -gstrict-dwarf.  For -gsplit-dwarf -gdwarf-5 use
	DW_MACRO_*_strx instead of DW_MACRO_*_strp.  Handle
	DW_MACRO_define_strx and DW_MACRO_undef_strx.
	(save_macinfo_strings): Use DW_MACRO_*_str* even with
	-gdwarf-5 -gstrict-dwarf.  Handle DW_MACRO_define_strx and
	DW_MACRO_undef_strx.