gettext:po_to_json runs twice during source install

Problem to solve

The source install docs have a step to run

sudo -u git -H bundle exec rake gettext:compile RAILS_ENV=production

The exact same output scrolls past me a bit later during the gitlab:assets:compile task, too, though. This seems inefficient, since the gettext:po_to_json task that both run takes about two minutes. Shaving of two minutes from a build seems significant to me.

I'm not sure what the best way forward is, deleting the gettext:compile from the documentation or fixing gitlab:assets:compile in some way, since gettext:compile also touches a file that seems to be used for some dependency tracking during the build, as mentioned here

Proposal

Make sure that gettext:po_to_json is only run once during build and make builds (for source installs at least) faster.