Recently, I wanted to use 'numpy' from the python environment inside my cygwin installation. I had python version 3.8 and also had python38-devel and libopenblas installed already. I even made sure that my cygwin version is >= 3.3. Even after this, my attempt at installing numpy using python3 -m pip install numpy failed with the following error:

      Run-time dependency openblas found: NO (tried pkgconfig and cmake)
      Run-time dependency openblas found: NO (tried pkgconfig and cmake)

      ../../numpy/meson.build:207:4: ERROR: Problem encountered: No BLAS library detected! Install one, or use the `allow-noblas` build option (note, this may be up to 100x slower for some linear algebra operations).

In the end, I noticed that there's already a python38-numpy package in the cygwin repo. I was able to install that package successfully and after that, I could use numpy from my python3.8 REPL!