Add a CMake based system for integration tests

[certik]

It tests CPython, LPython/LLVM and LPython/C. One invokes it using:

• CPython: cmake .
• LPython/LLVM: cmake -DLPYTHON_BACKEND=llvm .
• LPython/C: cmake -DLPYTHON_BACKEND=c .

Then one does make and ctest.

It should be equivalent to the previous testing script.

[certik]

@czgdp1807 After this is merged, simply add c to a given test and you'll see failures, the most common is that in C we need to forward declare functions (unlike C++). I haven't tested adding extra C files to link, but it will not be difficult.

If you want, you can try to get as many tests working with c as possible. It will require fixes in the C backend. I added one test that works with c, to ensure at least simple things work.

[certik]

@czgdp1807 regarding this PR, would you mind please testing locally by hand as well? This is a big change in our infrastructure, so to ensure it works.

[czgdp1807]

If you want, you can try to get as many tests working with c as possible. It will require fixes in the C backend. I added one test that works with c, to ensure at least simple things work.

Cool. Sounds good.

would you mind please testing locally by hand as well? This is a big change in our infrastructure, so to ensure it works.

Okay. On it right now.

[certik]

The failure on Linux and macOS at the CI is:

[  1%] Generating exit_01.o
python: can't open file '/usr/share/miniconda/envs/test/bin/../share/lpython/lib/lpython_parser.py': [Errno 2] No such file or directory
The command 'python /usr/share/miniconda/envs/test/bin/../share/lpython/lib/lpython_parser.py exit_01.py' failed.

Not sure if this path is not there at the CI anymore, or what the problem could be.

[czgdp1807]

Works on my mac as well. All tests pass.

[czgdp1807]

I check the CI on my debug commit and found out the following,

Inside, /usr/local/miniconda/envs/test/bin/../share/ lpython is in ~/work/lpython/lpython/integration_tests but we are executing python command over, /usr/local/miniconda/envs/test/bin/../share/lpython/lib/lpython_parser.py but we should be doing, /usr/local/miniconda/envs/test/bin/../share/~work/lpython/lib/lpython_parser.py (see the extra ~work).

See the logs at https://github.com/lcompilers/lpython/runs/6814568188?check_suite_focus=true

[certik]

I see, thanks! I think we are executing LPython from the wrong directory it seems, which then causes it to prepend wrong paths.

[czgdp1807]

Tests pass. 🎉.