I need to do this temporarily because we are using 'build_type' already on a table, and the way that it is defined prevents me from just remapping the type over to the enum. 

Ultimately, we'll get rid of it once the code that is using the existing build_type column in `product_versions` is updated to use the enum instead of a `citext` column, which is the source of our problems with many of these fields (the occasionally mixed case of build_type).