[nrf toup][nrfconnect] Fix zap-generate -o path argument

Fix `-o` path argument to be relative to `.zap` file's location
instead of Matter library's location.

Signed-off-by: Maciej Baczmanski <maciej.baczmanski@nordicsemi.no>

scripts/west/zap_generate.py

@@ -49,7 +49,7 @@ def do_run(self, args, unknown_args):
             raise CommandError("No valid .zap file provided")
 
         if args.output:
-            output_path = args.output
+            output_path = zap_file_path.parent / args.output
         else:
             output_path = zap_file_path.parent / "zap-generated"