Zerg's evolution chamber, Protoss' forge, and Terran's engineering bay have similar roles. All are pre-requisites for anti-air and detection buildings for the respective races.
What collective term or phrase could be used for these three structures?
Example scenario: You are playing a team game (with some inexperienced friends) and you spot a Twilight Council in production (implying the need for detection). Instead of saying "guys, better start building your evo chamber, forge, or e-bay", I would like to shorten it to something like "guys, better start building your insert collective name here."