runtime(glvs): fix a few issues

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>
diff --git a/runtime/plugin/getscriptPlugin.vim b/runtime/plugin/getscriptPlugin.vim
index 6029b65..f3abdbe 100644
--- a/runtime/plugin/getscriptPlugin.vim
+++ b/runtime/plugin/getscriptPlugin.vim
@@ -23,7 +23,7 @@
  endif
  finish
 endif
-let g:loaded_getscriptPlugin = "v36"
+let g:loaded_getscriptPlugin = "v37"
 let s:keepcpo                = &cpo
 set cpo&vim