Update Makefile so tests run on Raspberry Pi don't fail due to resource constraints.

[dave-ct]

Summary

When running pytest on a raspberry PI after creating the python-bindings, using all the threads causes the workers to crash and for some tests to fail.

Problem to solve

Change the number of threads to 1 when running tests on raspberry pi

Proposals

Update the frontends/concrete-python/Makefile and change pytest-default to detect if it is running on a raspberry pi. Example of update to pytest-default could be:

pytest-default:
        export LD_PRELOAD=$(RUNTIME_LIBRARY)
        export PYTHONPATH=$(BINDINGS_DIRECTORY)
        @# Check if running on Raspberry Pi
        @if grep -q 'Raspberry Pi' /proc/cpuinfo; then \
                echo "Running on Raspberry Pi, setting pytest threads to 1."; \
                PYTEST_THREADS=1; \
        else \
                PYTEST_THREADS=auto; \
        fi; \
        pytest tests -svv -n $$PYTEST_THREADS \
                --cov=concrete.fhe \
                --cov-fail-under=95 \
                --cov-report=term-missing:skip-covered \
                --key-cache "${KEY_CACHE_DIRECTORY}" \
                -m "${PYTEST_MARKERS}"

[BourgerieQuentin]

That's a bit invasive that put that in the makefile of the project. You can directly use the pytests command that you want outside of the makefile.