Allow tools/build to work for DIRDEPS_BUILD

[sjg]

Summary

We want to be able to build some host tools for non-FreeBSD hosts
without building more than we need. The DIRDEPS_BUILD lets us
do that.

We use the pseudo MACHINE "host" when building
for the host - deal with that when setting _host_arch.

Stage necessary headers from cross-build/include/common
so that tools like makefs need minimal change.

If .MAKE.OS is Linux we have additional work.

cross-build/include/common/grp.h if SETGROUPENT_IMPL is defined
actually generate the function - so its address can be taken (needed
by pwcache.c)

cross-build/fflags.c needs sys/types.h

cross-build/include/common/sys/cdefs.h gets nullability support

cross-build/mkimg/Makefile remove MK_STAGING=no as that prevents
getting the right -Is during DIRDEPS_BUILD

Sponsored by: Juniper Networks, Inc.

[sjg]

We are unlikely to be using host32 on FreeBSD

[sjg]

Stage common sys/_types.h too

[sjg]

mkimg needs Makefile.depend.options to get libegacy

[jrtc27]

Why are any of these tools/build/cross-build changes needed? Non-dirdeps does not need these. Fix your dirdeps build to match that case.

[sjg]

Add comments to linux sys/_types.h

[sjg]

In D39751#904733, @jrtc27 wrote:

Why are any of these tools/build/cross-build changes needed? Non-dirdeps does not need these. Fix your dirdeps build to match that case.

Again, the non-dirdeps build depend on side effects of multiple targets - it doesn't even *have* a standalone target to build any of this.

[jrtc27]

In D39751#904737, @sjg wrote:

In D39751#904733, @jrtc27 wrote:

Why are any of these tools/build/cross-build changes needed? Non-dirdeps does not need these. Fix your dirdeps build to match that case.

Again, the non-dirdeps build depend on side effects of multiple targets - it doesn't even *have* a standalone target to build any of this.

But you should make sure to use the same set of headers, compatibility files and compiler flags, then you won't need any changes to source files, just dirdeps build system bits to arrange things to match. The fact that you have to make changes to them points at the dirdeps environment being fundamentally different in ways that it shouldn't be.

[sjg]

Again, the non-dirdeps build depend on side effects of multiple targets - it doesn't even *have* a standalone target to build any of this.

But you should make sure to use the same set of headers, compatibility files and compiler flags, then you won't need any changes to source files, just dirdeps build system bits to arrange things to match. The fact that you have to make changes to them points at the dirdeps environment being fundamentally different in ways that it shouldn't be.

So I just did a buildworld (clean tree) on this Ub20 box, it did not finish, but produced mkimg at least. From which it is clear that tools/build/cross-build/mkimg/Makefile isn't used, as none of the CFLAGS it adds are present and there is no expand_number.o produced. I was surprised at the order of -I's used:
`-I/b/sjg/work/FreeBSD/sb/obj/b/sjg/work/FreeBSD/sb/src/amd64.amd64/tmp/legacy/usr/include
-DHAVE_NBTOOL_CONFIG_H=1
-I/b/sjg/work/FreeBSD/sb/src/tools/build/cross-build/include/common
-I/b/sjg/work/FreeBSD/sb/src/tools/build/cross-build/include/linux
-D_GNU_SOURCE=1`
47 -Wno-* flags might have something to do with it

Also odd tools/build has ${SRCTOP}/include/getopt.h in INCS but it is the getopt.h from libnetbsd that is actually getting used

[jrtc27]

If you build with -DWITH_DISK_IMAGE_BOOTSTRAP_TOOLS or whatever I called it you will also get makefs (and etdump).

[sjg]

Reduce to minimal change

[sjg]

Fix grammar in comment

[sjg]

Lose tar bits for now

[jrtc27]

LGTM with an appropriate commit message