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/compat/sys/null.h

@@ -0,0 +1,3 @@
+/*	$NetBSD: null.h,v 1.1 2007/07/19 13:49:12 jmmv Exp $	*/
+
+#include "../../../sys/sys/null.h"

tools/compat/sys/queue.h

@@ -0,0 +1,3 @@
+/*	$NetBSD: queue.h,v 1.1 2002/01/21 20:04:37 tv Exp $	*/
+
+#include "../../../sys/sys/queue.h"

tools/compat/sys/rmd160.h

@@ -0,0 +1,3 @@
+/*	$NetBSD: rmd160.h,v 1.1 2006/10/27 22:32:45 mrg Exp $	*/
+
+#include "../../../sys/sys/rmd160.h"

tools/compat/sys/sha1.h

@@ -0,0 +1,5 @@
+/*	$NetBSD: sha1.h,v 1.1 2006/10/29 06:17:08 dogcow Exp $	*/
+
+/* We unconditionally use the NetBSD SHA1 in libnbcompat. */
+#include "nbtool_config.h"
+#include "../../sys/sys/sha1.h"

tools/compat/sys/sha2.h

@@ -0,0 +1,3 @@
+/*	$NetBSD: sha2.h,v 1.1 2006/10/27 22:32:45 mrg Exp $	*/
+
+#include "../../../sys/sys/sha2.h"

tools/compat/sys/verified_exec.h

@@ -0,0 +1,3 @@
+/*	$NetBSD: verified_exec.h,v 1.1 2006/12/20 22:03:20 agc Exp $	*/
+
+#include "../../sys/sys/verified_exec.h"