#include <fontconfig/fontconfig.h> void FcConfigSetSysRoot (FcConfig *config, const FcChar8 *sysroot);
Set 'sysroot' as the system root directory. fontconfig prepend 'sysroot' to the cache directories in order to allow people to generate caches at the build time. Note that this causes changing current config. i.e. this function calls FcConfigSetCurrent() internally.
Fontconfig version 2.11.0