[3.0] freetype: darwin: fix font index issue

Fix VLCKit#635

In macOS/iOS/tvOS, font collection file contains multiple fonts. The 0 index should not be used by default, but the corresponding index should be used. This will fix some font rendering bugs and fallback font bugs.

This will also affect other projects using VLCKit

Related issues:

• https://github.com/jellyfin/Swiftfin/issues/497