從 5.2.1-RELEASE 要弄到 5-current 的時候, 發生 make error, +for 不認識.
記一下 -DALWAYS_CHECK_MAKE

/usr/src/UPDATING 這麼說的

To build a kernel
—————–
If you are updating from a prior version of FreeBSD (even one just
a few days old), you should follow this procedure. With a
/usr/obj tree with a fresh buildworld,
make -DALWAYS_CHECK_MAKE buildkernel KERNCONF=YOUR_KERNEL_HERE
make -DALWAYS_CHECK_MAKE installkernel KERNCONF=YOUR_KERNEL_HERE

References:

• Upgrade to 5.3-BETA1: make installkernel - Stop in /usr/src/sys/modules
  http://lists.freebsd.org/pipermail/freebsd-current/2004-August/035255.html
  Christian Hiris 4711 at chello.at
  Tue Aug 24 07:41:23 PDT 2004