Common baseos for all host land models?

[glemieux]

I'm thinking we should try and keep a common baseos build that is usable for both clm and elm host land models. In migrating the baseos files over from https://github.com/serbinsh/ctsm_containers, I've kept them all in the common baseos folder. If there are host land model specific builds, I propose that we work off of the baseos as much as possible until they significantly diverge.

[glemieux]

Baseos files are currently migrated per #11, but need explicit testing to see if they'll work for all HLMs.