PKGDIR和ports安装时"missing pkg-descr"的错误

在设置了PKGDIR之后，用ports安装时，会出现”找不到pkg-descr”的错误。

比较好的解释：

Things to check:

* /etc/make.conf -- you may have some variables defined in there
  which are breaking things.
* Make sure you're not setting MASTERDIR or PKGDIR or DESCR
  anywhere.
* Whether or not you have a shell alias for "make"
* If your /usr/ports/Mk/* files are corrupt or invalid in
  some way.  Here's a list of current ones as of Wed 13 Dec 2006
  20:33:19 PST and their MD5s:

MD5 (bsd.apache.mk) = 32a8cd8b9f3337a2c35df41800da134d
......
MD5 (bsd.sites.mk) = 2999f8a8d4808c499fdfa181ea03132e
MD5 (bsd.tcl.mk) = 23d63e131f626c18ed9ed103068242c1
MD5 (bsd.wx.mk) = 26500dc55d68571e1ae15f79a5ac916f

The Mk/bsd.port.mk code that's spitting out the error:

 574 # PKGDIR        - A directory containing any package creation files.
 575 #                 Default: ${MASTERDIR}

1368 PKGDIR?=        ${MASTERDIR}

2277 DESCR?=         ${PKGDIR}/pkg-descr

5397 .if !target(generate-plist)
5398 generate-plist:
5399     @${ECHO_MSG} "===>   Generating temporary packing list"
5400     @${MKDIR} `${DIRNAME} ${TMPPLIST}`
5401     @if [ ! -f ${DESCR} ]; then ${ECHO_CMD} "** Missing pkg-descr for ${PKGNAME}."; exit 1; fi