Bug 1678663 - Swallow exceptions during shutdown of fix_stacks.py, r=bc

Under Python 3 on Windows we sometimes get an OSError which may be a
race with the process exiting. There's not much we can do about
exceptions during shutdown so just ignore them.

Differential Revision: https://phabricator.services.mozilla.com/D99434

tools/rb/fix_stacks.py

@@ -67,8 +67,12 @@ def fixSymbols(
         # because it is more forceful than `wait()`, and the Python docs warn
         # about possible deadlocks with `wait()`.
         def cleanup(fix_stacks):
-            fix_stacks.stdin.close()
-            fix_stacks.terminate()
+            for fn in [fix_stacks.stdin.close, fix_stacks.terminate]:
+
+                try:
+                    fn()
+                except OSError:
+                    pass
 
         atexit.register(cleanup, fix_stacks)