Add retry mitigation suggested for apacheGH-40121

ci/scripts/cpp_test.sh

@@ -86,6 +86,7 @@ ctest \
     --label-regex unittest \
     --output-on-failure \
     --parallel ${n_jobs} \
+    --repeat until-pass:3 \  # Mitigation for GH-40121
     --timeout ${ARROW_CTEST_TIMEOUT:-300} \
     "${ctest_options[@]}" \
     "$@"