Set errno in adjtime if newlib time funcs are not implemented

Other time functions (e.g. settimeofday) set errno to ENOSYS if
IMPL_NEWLIB_TIME_FUNCS is not set.
adjtime should probably do the same.

components/newlib/time.c

@@ -139,6 +139,7 @@ int adjtime(const struct timeval *delta, struct timeval *outdelta)
     }
     return 0;
 #else
+    errno = ENOSYS;
     return -1;
 #endif
 }