Installing mariadb from opam on FreeBSD

If this happens:

% opam install mariadb
[...]
<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
[ERROR] The compilation of mariadb failed at
        "/usr/home/albert/.opam/ocaml-base-compiler/.opam-switch/build/mariadb.1.1.4/./configure
        --prefix=/usr/home/albert/.opam/ocaml-base-compiler".

#=== ERROR while compiling mariadb.1.1.4 ======================================#
# context     2.0.4 | freebsd/x86_64 | ocaml-base-compiler.4.09.0 | pinned(git+file:///usr/home/albert/ocaml-mariadb#master#b87c191b)
# path        /usr/home/albert/.opam/ocaml-base-compiler/.opam-switch/build/mariadb.1.1.4
# command     /usr/home/albert/.opam/ocaml-base-compiler/.opam-switch/build/mariadb.1.1.4/./configure --prefix=/usr/home/albert/.opam/ocaml-base-compiler
# exit-code   1
# env-file    /usr/home/albert/.opam/log/mariadb-79214-6cc03f.env
# output-file /usr/home/albert/.opam/log/mariadb-79214-6cc03f.out
### output ###
# Could not detect a MariaDB client library

The first problem is that configure tries to use gcc, which you probably don't have installed, and shouldn't be using anyway for compiling OCaml libraries. So link gcc to cc somewhere:

ln -s /usr/bin/cc ~/bin/gcc

The second problem is that configure doesn't manage to find the MariaDB libraries because it doesn't look in the right places (or use mysql_config as it should). So use this instead:

CPATH="/usr/local/include/mysql:/usr/local/include/mysql/mysql:/usr/local/include" \
LIBRARY_PATH="/usr/local/lib/mysql:/usr/local/lib" \
opam install mariadb

That should make it work.