PHP's pecl-mongodb fails to build with libbson 1.14.0:
checking for pkg-config... /usr/bin/pkg-config
checking for libbson... configure: error: system libbson must be upgraded to version >= 1.13.0

It's because the pkg-config files of libbson report version 0.0.0 being installed.

— mongo-c-driver-1.13.1/src/libbson/libbson-1.0-config.cmake 2019-03-18 08:13:11.245695549 +0100
+++ mongo-c-driver-1.14.0/src/libbson/libbson-1.0-config.cmake 2019-03-18 08:35:53.204418839 +0100
-set (BSON_MAJOR_VERSION 1)
-set (BSON_MINOR_VERSION 13)
-set (BSON_MICRO_VERSION 1)
-set (BSON_VERSION 1.13.1)
+set (BSON_MAJOR_VERSION 0)
+set (BSON_MINOR_VERSION 0)
+set (BSON_MICRO_VERSION 0)
+set (BSON_VERSION 0.0.0)

Also tried the master branch, same version 0.0.0.