Remove unused standard library glue

firmware/startup.c

@@ -217,51 +217,3 @@ void ResetHandler(void)
     while (1) ;
 }
 
-char *__brkval = (char *)&_ebss;
-
-void * _sbrk(int incr)
-{
-    char *prev = __brkval;
-    __brkval += incr;
-    return prev;
-}
-
-int _read(int file, char *ptr, int len)
-{
-    return 0;
-}
-
-int _write(int file, char *ptr, int len)
-{
-    return 0;
-}
-
-int _close(int fd)
-{
-    return -1;
-}
-
-int _lseek(int fd, long long offset, int whence)
-{
-    return -1;
-}
-
-void _exit(int status)
-{
-    while (1);
-}
-
-void __cxa_pure_virtual()
-{
-    while (1);
-}
-
-int __cxa_guard_acquire (int *g) 
-{
-    return 1;
-}
-
-void __cxa_guard_release(int *g)
-{
-}
-