py37-numpy @1.20.1 fails to build: "Running cythonize failed!"

[MarinosK (Marinos Koutsomichalis)]

py37-numpy @1.20.1 fails to build (Mac Ox Catalina 10.15.17), the tail of the log follows:

:info:build Running from numpy source directory.
:info:build Cythonizing sources
:info:build Traceback (most recent call last):
:info:build   File "setup.py", line 513, in <module>
:info:build     setup_package()
:info:build   File "setup.py", line 493, in setup_package
:info:build     generate_cython()
:info:build   File "setup.py", line 290, in generate_cython
:info:build     raise RuntimeError("Running cythonize failed!")
:info:build RuntimeError: Running cythonize failed!
:info:build Command failed:  cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-numpy/py37-numpy/work/numpy-1.20.1" && /opt/local/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7 setup.py --no-user-cfg build -j8
:info:build Exit code: 1
:error:build Failed to build py37-numpy: command execution failed
:debug:build Error code: CHILDSTATUS 81682 1
:debug:build Backtrace: command execution failed
:debug:build     while executing
:debug:build "system {*}$notty {*}$nice $fullcmdstring"
:debug:build     invoked from within
:debug:build "command_exec build"
:debug:build     (procedure "portbuild::build_main" line 8)
:debug:build     invoked from within
:debug:build "$procedure $targetname"
:error:build See /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-numpy/py37-numpy/main.log for details.

I tried with different compilers: +clang37 won't work (I get a message that this is not supported after Mojave); gfortran, gcc10, gcc9, and gcc8 all fail in the very same fashion.