[3.0] mac: Support macOS 10.7 with recent SDKs

On macOS 10.7, CFNetwork is not a separate framework, but it is contained inside CoreServices umbrella framework. Starting from 10.8, CFNetwork is a separate network (and thus those patches are only required on 3.0.x branch).

Goal of those very simple patches is to provide "best effort" support for Mac OS X 10.7 as minimum version, even if we choose a modern SDK + dev environment to compile VLC. (Modern == SDK >= 10.15). On those SDKs, CFNetwork is always linked directly by default. This shall support the move of our dev + CI environments to more modern macOS versions and SDKs.

Tested with compilation on macOS Monterey (macOS 13 SDK (Ventura), cross compiling for intel64): -> Runs fine on macOS 10.7.