In my particular case no, it would be too much hassle for a small business like ours (we are a remote only firm with only a few people). But I can imagine it would make sense when we grow.
There is no cloud service for that ... except Google Cloud Build.
Are you aware of anyone using it for C++? I couldn't find any mention of C++ in the documentation nor via Googling (sure it will be possible but it seems to involve significant setup)
In many companies the build cluster runs on the developers' workstations themselves, which has the benefit of fully using idling machines. The drawback is higher maintenance due to less reliability of such machines.
Would your company accept internal hosting for such a cluster, i.e. paying for the hardware themselves?