util/glsl2spirv: fix type error in argument handling

args.Olib is set to `store_true`, which means it will always be `True`
or `False`, this means that the we always, unconditionally, add
`--keep-uncalled` to the command line.

fixes: 9786d9ef2a

Reviewed-by: Luis Felipe Strano Moraes <luis.strano@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19449>

src/util/glsl2spirv.py

@@ -129,7 +129,7 @@ def process_file(args):
 
         cmd_list = ["glslangValidator"]
 
-        if args.Olib is not None:
+        if args.Olib:
             cmd_list += ["--keep-uncalled"]
 
         if args.vn is not None: