Investigate necessity of HAVE_DYLD_SHARED_CACHE_CONTAINS_PATH on macOS 11

According to https://github.com/indygreg/PyOxidizer/issues/373#issuecomment-792295106 the HAVE_DYLD_SHARED_CACHE_CONTAINS_PATH feature is required on macOS 11 for things to be happy.

I had unconditionally disabled that feature flag thinking it was an optional feature.

We should probably only conditionally disable on target SDK < 11.0.

But according to @ronaldoussoren it might be required to use ctypes when **running** on macOS 11?! If so, then the current builds are busted, as Python 3.8 uses the 10.15 SDK and 3.9 - while using the 11.0 SDK - has the feature disabled.