Mark set_times as unavailable for RTEMS target

Author: thesummer

library/std/src/sys/fs/unix.rs

@@ -2166,7 +2166,7 @@ fn open_from(from: &Path) -> io::Result<(crate::fs::File, crate::fs::Metadata)>
 
 fn set_times_impl(p: &CStr, times: FileTimes, follow_symlinks: bool) -> io::Result<()> {
     cfg_select! {
-       any(target_os = "redox", target_os = "espidf", target_os = "horizon", target_os = "nuttx", target_os = "vita") => {
+       any(target_os = "redox", target_os = "espidf", target_os = "horizon", target_os = "nuttx", target_os = "vita", target_os = "rtems") => {
             let _ = (p, times, follow_symlinks);
             Err(io::const_error!(
                 io::ErrorKind::Unsupported,