Cygwin - does not check that you can unzip

[tomaslin]

Unzip is not installed by default in cygwin.

When trying to install a new grails version, you get

Downloading: grails 1.3.8 from:


  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 46.2M  100 46.2M    0     0   510k      0  0:01:32  0:01:32 --:--:-- 1370k

Installing: grails 1.3.8
/home/IE User/.gvm/bin/gvm: line 162: unzip: command not found
mv: cannot stat `/tmp/grails-1.3.8': No such file or directory
Done installing!

[marc0der]

This requires an extra check for the unzip command in the install script.

[marc0der]

Implemented the check for $(which unzip) in the install.sh