bugfix: build.sh cross-compile on NetBSD host
bugfix: build.sh cross-compile on NetBSD host

As kindly reported by Nishimura Toru, the fix is quite simple.

cf: https://groups.google.com/d/msg/minix3/v3yejSogDqY/0TZxzpIHOzUJ

Change-Id: Ibdba8847982e93872217a6e736f50d4c90630e7a

veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi