Detect Netlib (BLAS/LAPACK)

[ogrisel]

It would be useful to detect that netlib has been linked to the Python program even if netlib is not multi-threaded.

It can help maintainers of scientific Python libraries diagnose performance problems reported by users.

[rgommers]

+1 for this. I just wrote some docs on BLAS-related diagnostics for SciPy, and this "Netlib went missing" was one of the things noticed quickly: scipy/scipy#20315 (comment).