solver precompilation in tests blocks unnecessarily

[exaexa]

JuMP+Tulip JIT takes quite a bit of time (~50 secs here). In the tests, the main worker JITs this in test/base/solver.jl, the other workers start in FVA tests. That wastest 50 seconds because the JIT doesn't run in parallel althought it could.

Proposed solution

kick the solver tests off with something parallel, so that the precompilation is also parallel.

Outcome

hopefully -60s test time, much less skewed test timing.

[laurentheirendt]

maybe we can add Tulip to the base image?

[exaexa]

not sure if that helps, I've got tulip installed and precompiled and using it first time in jump in a "fresh" julia process takes ~60s nevertheless

[stelmo]

Can confirm, it takes forever the first time you use it

[laurentheirendt]

sure, but in the Docker image, we could freeze the state after using Tulip

[exaexa]

wait, you can transplant a running julia to the testing env?

[laurentheirendt]

let's try ...