[solvcon] find a way to resolve numpy support of extra_c_compile_args in build_ext.py

[tai271828]

When working on #98 , we realized that the latest numpy seems to change its distribution approach so
numpy/distutils/command/build_ext.py does not support
extra_c_compile_argsin the way we expected to cause the following error:

    /usr/lib/python3.8/site-packages/numpy/distutils/command/build_ext.py", line 380,
    in build_extension extra_cflags = ext.extra_c_compile_args or [] AttributeError:
    'Extension' object has no attribute 'extra_c_compile_args'
    make: *** [Makefile:84: legacy] Error 1                                           

We need to find a way to resolve this issue so the whole SOLVCON build stack could enjoy the latest numpy in the end.