Add Linux AArch64 wheel build support

[odidev]

Added linux aarch64 wheel build support.
Related to #17, @bstellato Could you please review this PR?

[CLAassistant]

All committers have signed the CLA.

[nrontsis]

+1

[mmiller-max]

+1

[nrontsis]

Until this gets merged, here's how I generate wheels locally:

Save the following as build-qdldl-wheel.sh in an empty folder

#!/bin/bash
# Builds a wheel for qdldl
set -eu  # Stop script if a line fails
QDLDL_VERSION=${1}
echo "Building qdldl==$QDLDL_VERSION"

# numpy is in "install_requires" of qdldl - perhaps we don't need to install oldest-supported-numpy that is typically
# recommended for build requirements. https://numpy.org/devdocs/dev/depending_on_numpy.html#build-time-dependency
# However we install it here to be conservative, instead of just relying on the latest version.
python3 -m pip install oldest-supported-numpy

git clone --recurse-submodules https://github.com/osqp/qdldl-python --depth=1 --branch v$QDLDL_VERSION
pushd qdldl-python
mkdir dist
# Using constraints.txt might not be necessary if the package specifies build requirements correctly
# However, I prefer to be conservative here and end up with loud errors, rather than generate packages
# that have compatibility issues.
python3 -m pip freeze > constraints.txt
python3 -m pip wheel --constraint constraints.txt --wheel-dir=./dist .
for wheel in dist/qdldl*; do
    auditwheel repair $wheel  # Inject solver's shared libraries to wheel
done
for wheel in wheelhouse/*.whl; do
    cp -rf $wheel /wheels/ # Copy repaired wheel to shared volume
done
popd

popd

and then run from within that folder:

export PYTHON_BIN=/opt/python/cp311-cp311/bin/python
export QDLDL_VERSION=0.1.5.post3
docker run -v $(pwd):/wheels --rm --platform=linux/aarch64 quay.io/pypa/manylinux_2_28_aarch64 /bin/bash -c "\
    ln -s ${PYTHON_BIN} /bin/python3 && \
    bash /wheels/build-qdldl-wheel.sh ${QDLDL_VERSION}"

The generated wheel should appear in the folder the above command was executed from.

[imciner2]

aarch64 linux wheels are now available on PyPi after the recent refactor of the CI pipelines.