Make openblas-build work on macOS

[termoshtt]

Split from #44 (comment) and merges #49 issue because it is resolved by introducing of openblas-build crate on Linux.

macOS support of openblas-build crate looks have several problems.

• https://github.com/blas-lapack-rs/openblas-src/runs/1399358056
  • thread 'build::tests::build_no_lapacke' panicked at 'assertion failed: shared_lib.has_lapack()', openblas-build/src/build.rs:308:9
  • Library file inspection seems not working correctly. Maybe difference in nm of GNU and BSD?
• https://github.com/blas-lapack-rs/openblas-src/runs/1399358064
  • lapacke_dggsvp_work.c:127:9: error: implicit declaration of function 'dggsvp_' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  • May default C std target of Apple clang causes?
• https://github.com/blas-lapack-rs/openblas-src/runs/1399358073
  • clang: error: unsupported option '-fopenmp': macOS's clang does not support OpenMP :<

[maoe]

I ran into the second error on macOS Big Sur with current master (87c6477). FWIW I was able to work around the issue by using a real gcc instead of the Apple's /usr/bin/gcc which is clang in disguise.

brew install gcc
CC=gcc-10 cargo test

[termoshtt]

We can test M1 macOS on CI #112 and I have MacBook. It's time to resolve this issue.