Harfbuzz symbols exposed

Hello,

Using the dynamic framework on iOS, the many exposed symbols seem to cause issues with apps using other libs with common dependencies with vlckit.

Initial issue: https://github.com/mfkl/libvlc-nuget/issues/12

nm shows a lot of symbols that should not be there (hevc, vp9, yuv etc).

Having a look at this but pretty unfamiliar with this stuff so any help is welcome...