The following benchmark builds ended with segfaults:
https://evergreen.mongodb.com/task/mongo_c_driver_perf_c_driver_benchmark_mongo32_BenchMarkTests_8744119d0293908358f3aec5e95b5534ca0c47c0_18_03_06_17_05_21
https://evergreen.mongodb.com/task/mongo_c_driver_perf_c_driver_benchmark_mongo32_BenchMarkTests_30085af2124de68fd5ad714309f3ea2688489dee_18_03_02_02_42_22

Unfortunately they aren't consistently breaking, and I didn't have any luck reproducing them.

Let's add a debug build side-by-side with backtracing enabled so the next time it fails we can get more info.