i386, debug: Default to -gdwarf-4 on Windows targets with broken ld.bfd [PR98860]

i386, debug: Default to -gdwarf-4 on Windows targets with broken ld.bfd [PR98860]

As mentioned in the PR, before the
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba6eb62ff0ea9843a018cfd7cd06777bd66ae0a0
fix from March 1st, PECOFF ld.bfd didn't know about .debug_loclists,
.debug_rnglists and other debug sections new in DWARF 5.  Unfortunately,
unlike for ELF linkers, that means the sections were placed in wrong
ordering with wrong VMA/LMA, so the resulting executables are apparently
unusable.

As that is pretty new change, newer than 2.35.2 or 2.36 binutils releases,
the following patch adds a workaround that turns -gdwarf-4 by default
instead of -gdwarf-5 if a broken linker is found at configure time.
Users can still explicitly play with -gdwarf-5 and either use a non-broken
linker or use custom linker scripts for the broken one, but at least
by default it should work.

2021-03-31  Jakub Jelinek  <jakub@redhat.com>

	PR bootstrap/98860
	* configure.ac (HAVE_LD_BROKEN_PE_DWARF5): New AC_DEFINE if PECOFF
	linker doesn't support DWARF sections new in DWARF5.
	* config/i386/i386-options.c (ix86_option_override_internal): Default
	to dwarf_version 4 if HAVE_LD_BROKEN_PE_DWARF5 for TARGET_PECOFF
	targets.
	* config.in: Regenerated.
	* configure: Regenerated.