py-pytorch @2.0.0 fails to build on < 10.15

[jmroot (Joshua Root)]

Example build failures:

• ​https://build.macports.org/builders/ports-10.14_x86_64-builder/builds/160350/steps/install-port/logs/stdio
• ​https://build.macports.org/builders/ports-10.13_x86_64-builder/builds/185668/steps/install-port/logs/stdio
• ​https://build.macports.org/builders/ports-10.12_x86_64-builder/builds/224324/steps/install-port/logs/stdio

The relevant error appears to be:

/opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_python_py-pytorch/py310-pytorch/work/pytorch-2.0.0/aten/src/ATen/native/mkldnn/MKLDNNConversions.cpp:315:17: error: use of undeclared identifier 'cblas_sgemm_pack_get_size'
      (int64_t)(cblas_sgemm_pack_get_size(CblasBMatrix, M, N, K) / sizeof(float) + 1);
                ^