blocker for issue940

TODO:
* Look at the CPLEX licenses
* Wait for response from IBM
* See if self-hosted runners are an option

I opened issue1001 for replacing buildbot by Github actions. There, we have to look into Windows support for CPLEX.

The Fast Downward wiki? I don't think we have anything there. I added a stub at
http://www.fast-downward.org/ForDevelopers/GithubActions to collect information on Github actions. I think filling the information there should be part of issue940.

I have no objections either. Do we need info on the wiki that says something about Github actions? Or perhaps we have that already?

I agree with Silvan.

We didn't do this for SoPlex neither; I think running LP solvers on Windows could belong to the new issue "replace buildbot by Github actions" which I suggested to open in issue940.

I agree, but if we close it, we should directly add an issue for running LP on windows with GitHub actions.

Similar in spirit to issue970 (Find a way to run SoPlex during Github actions), I would consider this issue done. The part with how to run LP solvers on Windows is another story which holds for all three LP solvers we want to support.

Any objections?

Add TODO: Find out how to compile the planner with CPLEX on Windows on the command line in GitHub Actions.

Indeed, that was a requirement by IBM, and of course it also makes sense.

Malte said that when running CPLEX in Github actions, we should make sure that everyone with admin access on the Github repo is registered in the IBM academic initiative.

I think this answer resolves all TODOs.

We got an answer from IBM:

"The Academic Initiative license doesn't restrict on which or how many machines you can run CPLEX.  So I don't see an issue with running it in GitHub. Of course, you should protect the software from unauthorized access, as all users running it must be registered in the Academic Initiative program."

Regarding the other alternative of running CPLEX in non-self-hosted github actions, I  managed to obtain the license (however, for version 12.10; we only tested up to version 12.9). After having a first look at the license, it seems to me that only §3 is related to what we are granted to do with the program, and it remains quite unspecific. Most of the other parts are related to judicial things as far as I understand. I'll have a closer look on Monday.

(Dockerfile uses now the github api)

Update about self-hosted runners:
Yes they would work!
- github workflow allows to assign jobs to specific (e.g. one for SOPLEX, 
CPLEX) self hosted runners
- job should not run on pull request due to security issues (arbitrary code of 
peoples PR should not be executed on our machines)
- I have a docker prototype that sets up a self hosted runner and registers it 
with the repository.

- Todo: To register a self-hosted runner, each runner gets its own access 
token. The prototype requires the user to enter those tokens manually. I am 
now able to use the github api and will tomorrow automate this.
- Todo (after the previous todo): let a docker magician improve the Dockerfile