make: ensure .MAKE.SAVE_DOLLARS is set.
This makes it possible for macros to be set so as to work correctly
whether .MAKE.SAVE_DOLLARS is "yes" (NetBSD) or "no" (bmake).
- Simplify processing by centralizing: no need to prefix all errors with
"%lu: %s: " and pass fname, lineno to each; do it in one place.
- Use emalloc and friends instead of homegrown xmalloc and friends.
A bit of MMU handling cleanup:
- BI_MMU_APOLLO does, in fact, mean the Apollo MMU for 68020 used on the
DN3000 and DN4000 machines.
- If we end up with an unknown MMU value, try to reconcile with machine
type and CPU type.
Move virt68k's bootinfo code to a generic m68k location with names
linux_bootinfo.[ch] (since that's what this data is compatible with).
Facilitates use by other m68k platforms in the future.
Also, don't bother installing the header file; nothing in userland needs it.
mk: drop old, now unused version of DTB generation
This was replaced by bsd.dtb.mk back in 2020.
Build-tested on evbarm-aarch64, evbarm-earmv7hf, riscv-riscv64, amd64,
and sparc64.