Make the CI test segfault fallback find the JUnit XML report (#74280)

When pytest exits with a segfault, run_ci_tests.sh is meant to check the
JUnit XML report and pass the job if every test actually passed. The
report path was read from RESULT_LOG_FILE, which nothing sets; under
`set -u` the script aborted with "unbound variable" instead, so the
fallback never ran and every segfault failed the job with exit code 1.

The checker also treated a <testsuite> element without child elements
as missing, because an ElementTree element with no children is falsy.

Generated-by: Claude Opus 5

scripts/in_container/check_junitxml_result.py

@@ -30,7 +30,7 @@ if __name__ == "__main__":
         with open(fname) as fh:
             root = ET.parse(fh)
         testsuite = root.find(".//testsuite")
-        if testsuite:
+        if testsuite is not None:
             num_failures = testsuite.get("failures")
             num_errors = testsuite.get("errors")
             if num_failures == "0" and num_errors == "0":

scripts/in_container/run_ci_tests.sh

@@ -28,6 +28,18 @@ set +e
 export PYTHONFAULTHANDLER="1"
 export PYTHONUNBUFFERED="1"
 
+# Breeze passes the JUnit XML path only as a pytest argument.
+RESULT_LOG_FILE=""
+for arg in "${@}"; do
+    if [[ ${arg} == --junitxml=* ]]; then
+        RESULT_LOG_FILE="${arg#--junitxml=}"
+    fi
+done
+# A report left by an earlier run would let a segfault pass the check below.
+if [[ -n ${RESULT_LOG_FILE} ]]; then
+    rm -f "${RESULT_LOG_FILE}"
+fi
+
 pytest "${@}"
 RES=$?