Make windows image size configurable

[nk2IsHere]

~$ winmin-setup

(winmin-setup:2529): Gtk-WARNING **: 15:54:55.723: Could not find signal handler 'on_stack_configure_event'.  Did you compile with -rdynamic?
ISOPATH: /home/nick/Downloads/Win10_2004_English_x64.iso
WARNING  The requested volume capacity will exceed the available pool space when the volume is fully allocated. (51200 M requested capacity > 50847 M available)
ERROR    The requested volume capacity will exceed the available pool space when the volume is fully allocated. (51200 M requested capacity > 50847 M available) (Use --check disk_size=off or --check all=off to override)
error: failed to get domain 'winmin-base'
NULL

Sometimes the size 51200M can't be allocated in the system
Maybe you should consider adding a cmdline parameter to set disk size?

Example:

winmin-setup --disk-size 30000M