[ios,macos] Darwin implementation of a CoreText-based LocalGlyphRasterizer.

- Changing font weight does not currently appear to be working.
 - Glyph metric extraction code not working; currently unused.

src/mbgl/renderer/renderer.cpp

@@ -10,9 +10,10 @@ Renderer::Renderer(RendererBackend& backend,
                    FileSource& fileSource_,
                    Scheduler& scheduler_,
                    GLContextMode contextMode_,
-                   const optional<std::string> programCacheDir_)
+                   const optional<std::string> programCacheDir_,
+                   const optional<std::string> localFontFamily_)
         : impl(std::make_unique<Impl>(backend, pixelRatio_, fileSource_, scheduler_,
-                                      contextMode_, std::move(programCacheDir_))) {
+                                      contextMode_, std::move(programCacheDir_), std::move(localFontFamily_))) {
 }
 
 Renderer::~Renderer() {