[Windows] the 'global' option of the install script installWin.cmd does not work

[michael0710]

The install script fails to install the plugin with the 'global' option if the script is not run as administrator. A check similar to the one in the linux script should be added to stop the script and add a meaningful error message.

However, even if the script is run as administrator, the script failes due to some weird luarocks error:

[string "src/luarocks/cmd.lua"]:209: bad error, expected string, got: nil
stack traceback:
        [C]: in function 'assert'
        [string "src/luarocks/cmd.lua"]:209: in upvalue 'die'
        [string "src/luarocks/cmd.lua"]:724: in function 'luarocks.cmd.run_command'
        [string "luarocks"]:34: in main chunk
        [C]: in ?

That same error occurs when a cmd is run as administrator and any luarocks command is called with the --global argument

LuaRocks version: 3.12.2