opts.Add(ListOption('winsys', 'winsys drivers to build', default_winsys,
['xlib', 'intel', 'gdi']))
+opts.Add(EnumOption('MSVS_VERSION', 'MS Visual C++ version', None, allowed_values=('7.1', '8.0', '9.0')))
+
env = Environment(
options = opts,
tools = ['gallium'],