[3.14] gh-146498: Ensure binary content is correctly processed in multi-arch iOS XCframeworks (GH-146499) (#146502)

Ensure that multi-arch libpython dylibs aren't copied into the app, and the
standard lib is always found for framework post-processing.
(cherry picked from commit 5684b3a04c6985e48b9a3d5394e3b7878901d6aa)

Co-authored-by: Russell Keith-Magee <russell@keith-magee.com>