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/compat_getopt.h

@@ -0,0 +1,17 @@
+/*      $NetBSD: compat_getopt.h,v 1.2 2007/11/08 20:30:59 christos Exp $ */
+
+/* We unconditionally use the NetBSD getopt.h in libnbcompat. */
+
+#if HAVE_GETOPT_H
+#include <getopt.h>
+#endif
+
+#define option __nbcompat_option
+#define getopt_long __nbcompat_getopt_long
+
+#undef no_argument
+#undef required_argument
+#undef optional_argument
+#undef _GETOPT_H_
+
+#include "../../include/getopt.h"