Recommend using `ccache`?

[andrjohns]

Summary:

There can a lot of repeated compilation across different Stan programs if the same templates are being instantiated. We could suggest using ccache to help reduce compile times?

Current Version:

v2.34.1

[WardBrian]

I thought ccache only cached object files? If so, the fact that we precompile main.o and have a precompiled header is probably already as good as you can get, but id be interested if you’ve tried it and seen even more speed ups

[andrjohns]

Hmm good point, I should actually do some testing. I'll have a look and see if there's a noticeable difference

[WardBrian]

@andrjohns did you have a chance to see if this made a difference?