Alter advancement allows bypassing unlocking legacy

[arobinson]

In 1.18.3 at least, if you pick "aware of legacy possessed" and then use "Alter advancement", the legacy advancement option appears. You can then select that or pick another skill and it still seems to allow you to pick legacy advancements later, but never requiring you to repick "aware of legacy possessed" again.

Happened at least with Vritra

[Dugy]

It works with any unit type. It looks like I introduced an even bigger exploit after fixing the previous legacy prescience bug.