BLD Sets minimal supported numpy version in pyproject.toml (scikit-learn#16823)

Author: BenjaminLiuPenrose

pyproject.toml

@@ -4,6 +4,11 @@ requires = [
     "setuptools",
     "wheel",
     "Cython>=0.28.5",
-    "numpy>=1.13.3",
+    "numpy==1.13.3; python_version=='3.6' and platform_system!='AIX'",
+    "numpy==1.14.5; python_version=='3.7' and platform_system!='AIX'",
+    "numpy==1.17.3; python_version>='3.8' and platform_system!='AIX'",
+    "numpy==1.16.0; python_version=='3.6' and platform_system=='AIX'",
+    "numpy==1.16.0; python_version=='3.7' and platform_system=='AIX'",
+    "numpy==1.17.3; python_version>='3.8' and platform_system=='AIX'",
     "scipy>=0.19.1",
 ]