MySQL fails to start on arch Linux. Fatal error: Can't open and lock privilege tables: Table 'mysql.user' doesn't exist
The arch wiki helped me solve this pretty quickly. 

Install mariadb, afterwards run the following command before starting the mariadb.service:  

mysql_install_db --user=mysql --basedir=/usr --datadir=/var/lib/mysql
mysql_secure_installation


Arch does not hold your hand, with this type of thing. 
I guess if you install mysql / mariadb from source this is expected. 

This answer also helped me to figure out what I was looking for.
https://stackoverflow.com/a/22179751/619760