check `siso summary`

This is to make sure that the command runs as intended and make more
verbose if it has some error.

Bug: b/312632221
Change-Id: I44b372452b37b744f6c02c5a2e34fafe3717e351
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5051585
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Auto-Submit: Takuto Ikuta <tikuta@chromium.org>
Reviewed-by: Junji Watanabe <jwata@google.com>
Commit-Queue: Junji Watanabe <jwata@google.com>

post_build_ninja_summary.py

@@ -371,8 +371,9 @@ def main():
             cmd.extend(["--step_types", args.step_types])
         if args.elapsed_time_sorting:
             cmd.append("--elapsed_time_sorting")
-        subprocess.run(cmd)
+        subprocess.run(cmd, check=True)
-    else:
+        return 0
+
     try:
         with open(log_file, "r") as log:
             entries = ReadTargets(log, False)