Recent versions of MariaDB (10.2 onwards) require use of an unbundled SSL library. While these versions will build just fine on our CentOS supported platforms, they cannot be built on macOS without adding an unbundled SSL library as a platform prereq.
GnuTLS is preferred by MariaDB, and seems the path of least resistance (indeed, for those running homebrew a brew install gnutls is all that is needed to make these versions of MariaDB buildable.)
There is recent pressure to modernize our MariaDB components because of platform compatibility issues concerning the DAX service containers that are being built for use on clusters at CC-IN2P3 and within the PDAC and NCSA. This RFC proposes that GnuTLS be added as a platform prereq on macOS, so that MariaDB components may be upgraded.