Fix errors on #15640 that:
* led to use the wrong vim runtime directory name if using powershell or
bash on windows.
* use a wrong pattern to detect the users runtime dir
* allow to use global variables to specify un-archive commands
closes: #15722
Signed-off-by: GuyBrush <miguel.barro@live.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>