Backport PR #37144 on branch 1.1.x: BLD: update build requirement for py39 #37135 (#37189)

Co-authored-by: Fangchen Li <[email protected]>

Author: simonjayhawkins

pyproject.toml

@@ -7,10 +7,11 @@ requires = [
     "Cython>=0.29.21,<3",  # Note: sync with setup.py
     "numpy==1.15.4; python_version=='3.6' and platform_system!='AIX'",
     "numpy==1.15.4; python_version=='3.7' and platform_system!='AIX'",
-    "numpy==1.17.3; python_version>='3.8' 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'",
+    "numpy==1.17.3; python_version=='3.8' and platform_system=='AIX'",
+    "numpy; python_version>='3.9'",
 ]
 
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