[build-system]
requires = ["Cython>=0.23", "numpy", "setuptools", "wheel"]

[build-system]
requires = ["Cython>=0.23", "oldest-supported-numpy", "setuptools", "wheel"]

Use oldest-supported-numpy as build dependency
Use oldest-supported-numpy as build dependency

Fixes incompatible numpy versions build vs runtime, as NumPy
v1.20 is binary incompatible with older versions.

See https://github.com/pypa/pip/issues/9542
