Fix USE_FREETYPE=0 build (#1800)
Fix USE_FREETYPE=0 build (#1800)

When USE_FREETYPE=0, the resolve_font() function was declared but never
called, generating a warning on some platforms.
OpenImageIO/oiio,lgritz/oiio,lgritz/oiio,OpenImageIO/oiio,OpenImageIO/oiio,lgritz/oiio,lgritz/oiio,OpenImageIO/oiio