Import NetBSD tools and build.sh

This commit finalizes support for cross compilation. The tools
directory are all links to the actual tools and are built on the
host system to build Minix. build.sh is the work horse that takes
care of all environment settings. It's slightly adjusted for Minix.
The /usr/src/Makefile has additional targets needed for cross
compilation.

tools/host-mkdep/Makefile

@@ -0,0 +1,28 @@
+#	$NetBSD: Makefile,v 1.10 2008/10/19 22:05:23 apb Exp $
+
+TIMESTAMP=	${TOOLDIR}/bin/${_TOOL_PREFIX}host-mkdep
+
+CLEANFILES+=	config.cache config.log config.status host-mkdep
+
+.include <bsd.hostprog.mk>
+
+# When host-mkdep is built, TOOL_AWK is not yet available, so we do not
+# pass AWK=${TOOL_AWK:Q} to configure; we allow configure to find awk
+# for itself (or complain if it can't find awk).
+
+realall: host-mkdep
+host-mkdep: configure host-mkdep.in
+	-rm -f $@
+	CC=${HOST_CC:Q} ${HOST_SH} ${.CURDIR}/configure --cache-file=config.cache
+	chmod +x $@
+
+# This is the only program that comes before binstall.
+install: ${TIMESTAMP}
+${TIMESTAMP}: host-mkdep
+	mkdir -p ${TOOLDIR}/bin
+	cp host-mkdep $@
+	chmod +x $@
+
+# Run by hand, then "configure" script committed:
+regen:
+	cd ${.CURDIR} && ${TOOLDIR}/bin/${_TOOL_PREFIX}autoconf