FcDirScan - scan a font directory without caching it
#include <fontconfig/fontconfig.h>
FcBool FcDirScan (FcFontSet *set, FcStrSet *dirs, FcFileCache *cache, FcBlanks *blanks, const FcChar8 *dir, FcBool force);
If cache is not zero or if force is FcFalse, this function
  currently returns FcFalse. Otherwise, it scans an entire directory and adds
  all fonts found to set. Any subdirectories found are added to
  dirs. Calling this function does not create any cache files. Use
  FcDirCacheRead() if caching is desired.