Automated build process with GitHub actions

[jimkring]

Support for Windows and Ubuntu builds:

- os: windows-2019
  cuda: "11.4.0"
  visual_studio: "Visual Studio 16 2019"
  python: "3.9"

- os: ubuntu-20.04
  cuda: "11.4.0"
  python: "3.9"

[jimkring]

@superchromix you can see the build jobs here: https://github.com/JKISoftware/Gpufit-Continuous-Integration/actions?query=branch%3Aautomated-build-process

[gpufit]

The build on linux is currently failing, but passing on windows. Confusing since I can’t see anything in the latest commits which could cause a linux-specific failure

[jimkring]

@gpufit I'm not sure why the python wheel isn't building.

That said, the cmake updates (from @ironictoo) in PR #94 fix the build -- I verified this in my own fork by merging PR #94 branch into the latest Gpufit main which triggered a CI build that worked just fine.

[ironictoo]

This is a problem using the deprecated find_package(pythonInterp) instead of find_package(python). Cmake is trying to use python 3.9.14 (the default Ubuntu version), and wheel gets setup on 3.9.15 (the version we install and configure). Probably the install python scripts were updated to version 3.9.15 in the last few days, but the default ubuntu install is still 3.9.14. I'm guessing before they were both on 3.9.14 before (when it worked) so it didn't matter if CMake screwed up, but now it does. This is because the old CMake function doesn't respect the common environment variables that are set to indicate the "correct" python to use.

As Jim said, this is fixed in PR #94