Add makefs to the list of bootstrap tools

[arichardson]

Summary

Having this as part of the bootstrap tools is useful to build disk images
to boot in QEMU (especially when building on a Linux/macOS host where
mkimg is not available). We have been bootstrapping makefs+mkimg in
CheriBSD for a long time (using LOCAL_XTOOL_DIRS) but I believe this
is also useful upstream.

Depends on D27602

[arichardson]

ping?

[emaste]

Makefile.inc1

2500

can we not just leave the dependency in place, if we don't actually need ${_bt}-lib/netbsd it won't matter?

[arichardson]

Drop unnecessary check

[emaste]

Looks OK to me, tiny concern is whether _libnetbsd= lib/libmd lib/libnetbsd could become out of sync (exists in two places)

[arichardson]

In D27619#646233, @emaste wrote:

Looks OK to me, tiny concern is whether _libnetbsd= lib/libmd lib/libnetbsd could become out of sync (exists in two places)

Yeah I don't like that either but I'm not sure if there's an easy way to avoid it.

[arichardson]

Add comment to keep the two assignments synchronized