ffmpeg/videotoolbox: protect UTGetOSTypeFromString on both VDA and VT

ffmpeg_videotoolbox.c

@@ -157,7 +157,13 @@ int videotoolbox_init(AVCodecContext *s)
             CFStringRef pixfmt_str = CFStringCreateWithCString(kCFAllocatorDefault,
                                                                videotoolbox_pixfmt,
                                                                kCFStringEncodingUTF8);
+#if HAVE_UTGETOSTYPEFROMSTRING
             vtctx->cv_pix_fmt_type = UTGetOSTypeFromString(pixfmt_str);
+#else
+            av_log(s, loglevel, "UTGetOSTypeFromString() is not available "
+                   "on this platform, %s pixel format can not be honored from "
+                   "the command line\n", videotoolbox_pixfmt);
+#endif
             ret = av_videotoolbox_default_init2(s, vtctx);
             CFRelease(pixfmt_str);
         }