From https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=853483, "libbson: ftbfs with GCC-7"
In the Debian build log, the last test that succeeds is "/endian/swap64", so the test that fails must be the next one, "/bson/iso8601/utc".
I rewrote the ISO8601 parser for
CDRIVER-1962, but it's unknown whether the test would have passed with GCC 7 before my rewrite or not.
GCC 7 is unreleased. I think we just need to fix this before Debian Buster with GCC 7 arrives, or other GCC 7 distributions. It's possible it's a new GCC bug that will be resolved without us.