On macOS, configure is unable to detect the installed OpenSSL library. When trying to configure the MongoDB C library with OpenSSL installed at a custom location (/usr/local/custom/openssl) specified in the PKG_CONFIG_LIBDIR (or PKG_CONFIG_PATH) environment variable, configure is unable to detect the installation and exits with an error: configure: error: You must install the OpenSSL development headers to enable OpenSSL support.

See the attachment for the commands and flags I used as well as the configure output.

I was previously able to use the same build procedure to get the 1.3.6 version of the Mongo C library to correctly configure and build.