Porting FlashFS to use NANDFlash

Hi,
I adopted FlashFS to use my NANDFlash (9F2G08U0A).
finit() and fformat ("F:") are working fine and the flash gets erased.
But if I call fopen, to create files, I get linker error:

.\at91sam9260-sdram\at91sam9260-sdram.axf: Error: L6915E: Library reports error: __use_no_semihosting_swi was requested, but _sys_open was referenced

I got a retarget.c which implements _sys_open and many other _sys-functions:

FILEHANDLE _sys_open (const char *name, int openmode) {
   /* Register standard Input Output devices. */
   if (strcmp(name, "STDIN") == 0) {
      return (STDIN);
   }
   if (strcmp(name, "STDOUT") == 0) {
      return (STDOUT);
   }
   if (strcmp(name, "STDERR") == 0) {
      return (STDERR);
   }
   return (__fopen (name, openmode));
}

How can I compile my code without errors?