build-essential install for Python extensions

[RobHooper]

@jpmckinney, build-essential was removed in #536 however it is still set to be installed in python/extensions.sls.

From my reading this is installed for kingfisher collect, is this dependency still needed?

The concern is that a python module has been installed using the build-essential libraries / tooling and will error next time it is updated or during a fresh deployment.

I noticed this running a test deployment on ocp27.
On ocp23 build-essential was re-installed earlier this month, most likely due to the above.

[jpmckinney]

Ah, yes, I meant to reinstall it on that server as well, after noticing the same thing. Done now.