Since libmd was added to the bootstrap, building main on stable/14
fails because of an incompatibility in its old md4.h.  Fix this by
always including md4.h in the bootstrap headers, instead of only
doing so when building on a non-FreeBSD host.

Fixes:		50de0bf50512 ("flua: Always build as a bootstrap tool")
Reported by:	olce
Reviewed by:	olce, kevans
Sponsored by:	https://www.patreon.com/bsdivy
Differential Revision:	https://reviews.freebsd.org/D56327

We could patch the tzcode config to not use it, but it's simple to
provide an implementation of it and avoid spreading cross-build
bootstrapping special cases.

Fixes:		ff2c98b30b57 ("tzcode: Update to 2026a")
MFC after:	1 week

Effort:		CHERI upstreaming
Sponsored by:	Innovate UK
Reviewed by:	kib
Co-authored-by:	Alfredo Mazzinghi <am2419@cl.cam.ac.uk>
Co-authored-by:	Alex Richardson <Alexander.Richardson@cl.cam.ac.uk>
Differential Revision:	https://reviews.freebsd.org/D55308

Summary:
The sys/cdefs.h in src is incompatible with glibc's sys/cdefs.h so
cross-building broke when the former was added to SYSINCS in 1c9ff80f06. This
commit adds a guard around that to only do that when building on FreeBSD. This
should fix github CI.

Test Plan:
Ran buildkernel using tools/build/make.py on linux in github CI and
locally on FreeBSD to double check nothing broke.

Reviewed by:    dim
MFC after:      3 days
Differential Revision: https://reviews.freebsd.org/D54385

This is needed since sys/cdefs.h includes sys/_visible.h.

Reported by:	kib
Fixes:		1c9ff80f0635
MFC after:	3 days

This is needed to let the legacy stage compile against newer versions of
sys/font.h, which transitively includes sys/cdefs.h, and requires the
new __nonstring macro from it.

Fixes:		e2c93ed09f25
MFC after:	3 days

We need to preserve modification times on bootstrap tools, but `cp -p`
also tries to preserve flags, which fails if OBJROOT is on NFS.  A -N
option was added to cp for this purpose, but trying to use that would
break cross-building on hosts that don't have that option.  The best
remaining option is `install -p`, which we already assume is present.

PR:		275030
Reviewed by:	imp, emaste
Differential Revision:	https://reviews.freebsd.org/D53751

This is needed when bootstrapping libc, reallocarray.c and
recallocarray.c include stdckdint.h now.

Reviewed by:	emaste
Fixes:	7233893e9496 ("lib{c,openbsd}: use ckd_mul() for overflow checking in re(c)allocarray")
Differential Revision:	https://reviews.freebsd.org/D52932

This version builds every module into the flua binary itself, since all
of the bootstrap tools are built -DNO_SHARED.  As a result, we also
cannot dlsym(), so we can't really discover the names of our newly
builtin modules.  Instead, just build out a linker set with all of our
luaopen_*() functions to register everything up-front.

Building in all of the modules isn't strictly necessary, but it means
that we have an example of how to add a bootstrap module everywhere you
go and one doesn't need to consider whether bootstrap flua can use a
module when writing scripts.  On my build machine, the consequence on
our binary size is an increase from around 1.6M -> 1.9M, which isn't
really that bad.

.lua modules can install into their usual path below $WORLDTMP/legacy
and we'll pick them up automagically by way of the ctor that sets up
LUA_PATH early on.

This re-lands bootstrap module support with a more sensible subset, and
after having verified that it cross-builds fine on macOS and Linux -- we
cannot do libfreebsd on !FreeBSD because it's more system header
dependant.  We also need to bootstrap libmd to bring in libhash, and
libucl + libyaml.

Reviewed by:	bapt, emaste (both previous version)
Differential Revision:	https://reviews.freebsd.org/D51890

This reverts commit 1953a12ee2cde1afacb3e3f7612d89695c96e04f, because it
cannot work at all on macOS without more work, at a minimum.  We use
linker sets for module discovery, but we don't have a version of this
that works for mach-o at the moment.