BUG: Fix cblas detection for the wheel builds

[seberg]

This is a mess and doesn't attempt to fix the issues around gh-24200, but it should fix the issue of our wheels not using CBLAS.

The suffix may be directly injected into the flags to get the define and there is also a tangle between HAVE_CBLAS and HAVE_LAPACK and we only probe the first.

I tried this locally by checking that if the define exist redefining it to nonesense gives the slow version.
(I cannot test the full thing without a prefixed blas locally, because setting the prefix will not avoid blas use in LAPACK meaning you don't use CBLAS, but the blas symbols used by lapack are missing)

---

CC @mattip and @rgommers, I do not plan to attempt the "full" fix, it seems that may require untangling the way these things are set. I think this works, but we may have to give it a roll to be sure probably.

[seberg]

OK, I downloaded and installed the artifact wheel locally and it seems fine.

[rgommers]

Thanks @seberg, that seems to do the job. At least I spot checked an x86-64 manylinux and an arm64 macOS wheel build, and both logs show:

Run-time dependency openblas found: YES 0.3.23.dev
Checking if "CBLAS" with dependency OpenBLAS: links: YES

This is a mess and doesn't attempt to fix the issues around gh-24200, but it should fix the issue of our wheels not using CBLAS.

Agreed it is messy. Longer term these checks should live in Meson and not here, so we can simply write something like:

openblas_dep = dependency('openblas',
  version : '>=0.3.21',
  language: 'c',
  modules: [
    'interface: ilp64',
    'symbol-suffix: 64_',
    'cblas',
  ]
)
# Query properties as needed:
has_cblas = openblas.get_variable('cblas')
is_ilp64 = openblas_dep.get_variable('interface') == 'ilp64'
blas_symbol_suffix = openblas_dep.get_variable('symbol-suffix')

and only express our actual build/dependency logic in our own meson.build files.

I'll need to finish up mesonbuild/meson#10921 within the next couple of months for that.

[charris]

Whoa, I added a label and the wheel builds restarted. Might be something a bit off in the triggering.

[charris]

Thanks Sebastian.