MariaDB: Fixed post-install failure on OS X 10.9

[deiga]

Added mkdir to create brew --prefix/etc/my.cnf.d
This prevents the post-install step of failing

Fixes #25140

[jacknagel]

It works fine for me without this change; we should try to determine the root cause before pulling this.

[jacknagel]

Hmm, I neglected to remove /usr/local/var/mysql first and so post_install wasn't actually running.

This is indeed the right fix, however it should probably done in install instead near this code:

https://github.com/mxcl/homebrew/blob/3872723ba2e5e3baa079826f7bb65dae49fbb50a/Library/Formula/mariadb.rb#L104-L107

and can simply be (etc/'my.cnf.d').mkpath.

[jacknagel]

Fixed by 935f8f1