MAINT: Fix build when using scipy-openblas wheels

[mattip]

The helper file will only be created when using spin --with-scipy-openblas. When using a workflow that builds from source, the helper file is not created and the build will fail:

pip install scipy-openblas32
python -c 'import scipy_openblas32; print(scipy_openblas32.get_pkg_config())' > ./scipy-openblas.pc
export PKG_CONFIG_PATH=$PWD
pip install  --no-binary :numpy: numpy==1.26.5

This should fix the problem. Skipping CI since this problem is not hit by current CI.

[mattip]

I don't know if another 1.26.x is planned, but if so it would be nice to have this.

[charris]

I don't know if another 1.26.x is planned

We can no longer make 1.26.x wheels for macosx m1. Cirrus upgraded the tool chain and fixing it seemed more work than justified by the accumulated backports.

[charris]

Thanks Matti, I put it in just in case.