Fix CPLEX compilation on Windows for repos not named 'downward'.

[jendrikseipp]

No description provided.

[FlorianPommerening]

Looks like there are two conflicting solutions: Getting rid of the hard-coded paths D:\a\downward\ and working around them.

[jendrikseipp]

Looks like there are two conflicting solutions: Getting rid of the hard-coded paths D:\a\downward\ and working around them.

Yes. I opted for the less intrusive one. Do you prefer the other one, i.e., using D:\a\cplex_temp and D:\a\cplex?

[FlorianPommerening]

I'm fine with using the environment variable but what I meant was that there are still places with the hard-coded paths. It would make sense to use the variable path everywhere instead of using hard-coded paths in some places and variable paths in others.

[jendrikseipp]

I now install CPLEX directly under D:\a\cplex, removing the need for the mkdir hack. Now I'm using env vars everywhere it's possible, I think. Good to merge now?

[FlorianPommerening]

That makes more sense now. The installation is still weird but I think all of that weirdness was there before (for example, the copy from cplex_temp to cplex because for some reason we cannot directly install to cplex). I'm fine with merging this.