Merge pull request matplotlib#23517 from meeseeksmachine/auto-backport-of-pr-23511-on-v3.5.x

Backport PR matplotlib#23511 on branch v3.5.x (supporting IBM i OS)

Author: QuLogic

setupext.py

@@ -197,9 +197,12 @@ def get_and_extract_tarball(urls, sha, dirname):
 options = {
     'backend': config.get('rc_options', 'backend', fallback=None),
     'system_freetype': config.getboolean(
-        'libs', 'system_freetype', fallback=sys.platform.startswith('aix')),
+        'libs', 'system_freetype',
+        fallback=sys.platform.startswith(('aix', 'os400'))
+    ),
     'system_qhull': config.getboolean(
-        'libs', 'system_qhull', fallback=False),
+        'libs', 'system_qhull', fallback=sys.platform.startswith('os400')
+    ),
 }