The -with-libbson and -with-libmongoc configure options were made obsolete by PHPC-1497 and later deprecated in PHPC-2311. They should be removed entirely in 2.0.
is related to
PHPC-1497Introduce new configure switch to use system libraries
Closed
PHPC-2311Note with-libbson and with-libmongoc deprecation in configure help text