MNT: Experimenting with openblas

Here I'm updating the fsl-base recipe so that it conforms to the recommendations in the conda-forge knowledge base.

We need to use openblas-openmp for the eddy-openmp build (https://github.com/xianyi/OpenBLAS/wiki/Faq#multi-threaded), but I'm not quite sure how to control which openblas variant is selected. I don't think it is possible to specify that in a recipe.

However, the pthread/openmp openblas variants should be binary compatible, right? So it shouldn't matter which variant is present at build time. Right?

I suspect that I will need to specify that we want the openmp build in the FSL release manifest.