Import irisboot, yet another bootloader for pre-ARC sgimips machines.

This bootloader adds support for Personal IRIS 4D/25 (IP6),
Personal IRIS 4D/35 (IP12), and Indigo R3000 (IP12) etc. and
optionally supports R4000 Indy and Indigo R4000 (ARCS machine)
using standalone WD33C93 SCSI driver.

Submitted by Naruaki Etomi via PR port-sgimips/53539,
and reviewed by tsutsui@. See also port-sgimips@ ML thread:
https://mail-index.netbsd.org/port-sgimips/2018/09/16/msg000778.html

branches: 1.24.12; 1.24.14;
centralize vers.c building for standalone programs.

branches: 1.23.2;
Avoid the PIE

branches: 1.22.6; 1.22.10;
Add empty LIBCRTI= as LIBCRT0 to build sa programs without installed DESTDIR.

XXX: probabry we should have bsd.saprog.mk or something.

branches: 1.21.4; 1.21.14; 1.21.18;
Make sure that sgimips64 can build the O32 bootloaders

Merge forward matt-nb5-mips64
Adapt to new interrupt/spl framework
Deal with arcbios calls being O32 and kernels being N32/N64.
Need to save/restore T8 across arcbios calls.

Define NOMAN earlier

Drop bootprog_maker (formerly enabled by -M) and bootprog_date (formerly
disabled by -D) from the output of newvers_stand.sh. Change -D to the
inverted logic, so that it adds the date to bootprog_rev in ().

Change all platforms accordingly. -D is added if MKREPRO is not yes and
wasn't present before. Platforms that didn't use -D don't depend on
MKREPRO now either.

branches: 1.17.4; 1.17.6; 1.17.8;
Merge from matt-nb5-mips64
Merge mips-specific arch files.

- use <bsd.klinks.mk> to create MD include dir symlinks
- make sure to remove lib subdirs on clean and distclean target

branches: 1.15.4; 1.15.12; 1.15.18; 1.15.22;
Enable warning options.

- use bootprog_name[] generated by sys/conf/newvers_stand.sh
- constify, KNF
- fix bootloader names in comment

branches: 1.13.50; 1.13.70; 1.13.74;
merge ktrace-lwp.

branches: 1.12.16;
Rationalize the machine-links creation mechanism.

Rework the boot loader:
* remove dead code,
* streamline kernel selection logic,
* various small bugfixes.

Use ${HOST_SH} instead of `sh'.

If necessary, pull in <bsd.sys.mk> to get the definition of HOST_SH;
Makefiles that pull in one of (most of) <bsd.*.mk> will get this anyway.

Define LIB{CRT0,C,CRTBEGIN,CRTEND} as nothing, we don't need to link
against them.

branches: 1.8.2;
also create boot.ip32 with the entry point set to the IP32 load address

from Chris Sekiya

Add "-mno-abicalls" to AFLAGS. Add "-ffreestanding -msoft-float" to
CFLAGS.

branches: 1.6.2;
Add -Dsgimips to CPPFLAGS.

MKfoo=no -> NOfoo

Nuke cleandir target override.

Note kernel load adress change.

- Clean up the bootloader Makefiles somewhat.
- Build an ECOFF version of the bootloader as "boot". As a temporary
measure (due to a bug in libbfd which has not yet been fixed, but
for which a work-around exists as a patch), install and ELF version
of the bootload as well as "boot.elf". "boot.elf" will go away once
the toolchain issue is resolved.

Initial cut at a bootloader for NetBSD/sgimips, by Michael Hitch.