[Green dragon] add a SIGINT handler to error when jenkins kills the process (#874)

Jenkins will kill the processes on stage timeouts via SIGINT, however we
ignore errors in the subprocesses to defer to the junit plugin, so
instead detect SIGINTS and exit with a nonzero exit

https://docs.python.org/3/library/signal.html#note-on-signal-handlers-and-exceptions

Author: justice-adams-apple

zorg/jenkins/build.py

@@ -12,10 +12,21 @@
 import math
 import re
 from pathlib import Path
+import signal
 
 import requests
 from contextlib import contextmanager
 
+_received_sigint = False
+
+
+def _sigint_handler(signum, frame):
+    global _received_sigint
+    _received_sigint = True
+
+
+signal.signal(signal.SIGINT, _sigint_handler)
+
 BUCKET = os.environ.get("S3_BUCKET")
 
 NINJA = "/usr/local/bin/ninja"
@@ -932,6 +943,8 @@ def run_cmd(working_dir, cmd, env=None, sudo=False, err_okay=False):
             subprocess.check_call(cmd)
             os.chdir(old_cwd)
         except subprocess.CalledProcessError as excpt:
+            if _received_sigint:
+                raise excpt
             if not err_okay and not ignore_errors_override:
                 raise excpt
             else: