Relevant note:
The clang4 build was failing because the algorithm for generating the starting base tries random layouts by adding and removing facilities. Removing living quarters while there are agents in the building should fail, therefore causing an error in the base generation.
It's possible for a starting base to have agents inside it if they are spawned as hireable agents (this happens during GameState::fillOrgStartingProperty). Moreover, there's nothing preventing a hireable agent to spawn inside an XCom base!
This edge case is dependent on the seed used in the rng. Here's one that causes such behaviour:

• Seed: 1545206368882

I've worked around this issue by generating the starting base (by calling GameState::fillPlayerStartingProperty) before the hireable agents are created.
A more complete fix should prevent agents to spawn from XCom bases or purchaseable buildings.

Building::investigate was renamed to Building::pendingInvestigatorCount in a505ea0
Eventually we should add a serializable state object to represent an ongoing investigation to allow multiple investigations in the same building and maybe vehicles