1.5.19: update-info-dir.sh error

[J.Chris Findlay]

Hi, I think this is the right place for this.

I noticed that every time /etc/postinstall/update-info-dir.sh runs, it
appends to the old dir info-entry, rather than replacing it.  (This
was happening every time I updated cygwin.)

Upon further investigation I noticed that the above script does a "rm
-f /usr/info/dir", but then writes it's output to
"/usr/share/info/dir" instead.

I believe this needs to be changed to "rm -f /usr/share/info/dir" to
correct the problem.
--
 - J.Chris Findlay
   (c: