Skip restart roundtrip check during --generate mode

The restart_check block ran unconditionally after golden file
generation, doubling wall-clock time for restart-flagged test
cases when using ./mfc.sh test --generate.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sbryngelson

toolchain/mfc/test/test.py

@@ -449,7 +449,7 @@ def _handle_case(case: TestCase, devices: typing.Set[int]):
 
         # Restart roundtrip verification: run to midpoint, restart,
         # and compare restarted output against the straight run.
-        if case.restart_check and not ARG("add_new_variables"):
+        if case.restart_check and not ARG("add_new_variables") and not ARG("generate"):
             straight_pack = pack
 
             if timeout_flag.is_set():