Change default cache location

apt-get uses /var/cache to store downloaded files

http://askubuntu.com/q/178806/where-do-packages-installed-with-apt-get-stored

This makes sense with Cygwin as well because Cygwin already has a /var/cache
which is almost empty to start, compared to /setup which does not exist outside
of apt-cyg.

apt-cyg

@@ -75,7 +75,7 @@ function findworkspace()
 {
   # default working directory and mirror
   mirror=http://mirrors.kernel.org/sourceware/cygwin
-  cache=/setup
+  cache=/var/cache
   
   # work wherever setup worked last, if possible
   if [ -e /etc/setup/last-cache ]