These have been build options since the waf build, but that doesn't
really make sense. The build can detect whatever macOS sdk version is
available and then use that information to determine whether to enable
the features or not. Potentially disabling multiple sdk versions doesn't
really make any sense. Because f5ca11e12b
effectively made macOS 10.15 the minimum supported version, we can drop
all of these checks and bump the required sdk version to 10.15. The rest
of the build simplifies from there.
this drops support for swift <4.1 and with this support for xcode <=9.2.
this was the last setup that is officially working on macOS 10.12.
our old legacy build macOS 10.12 + xcode 9.2 is replaced by macOS 10.13
+ xcode 9.4.1 with swift 4.1. the macOS 10.13 + xcode 10.1 VM is
replaced by the latest macOS 10.14 + xcode 11.3.1 VM. this is the oldest
version officially supported by Apple.
this is in preparations for the following commit.
all the get_property_* usages were removed because in some circumstances
they can lead to deadlocks. they were replaced by accessing the vo and
mp_vo_opts structs directly, like on other vos.
additionally the mpv helper was split into a mpv and libmpv helper, to
differentiate between private and public APIs and for future changes
like a macOS vulkan context for vo=gpu.
