od: port GNU stdin compatibility to wasi

Author: oech3

src/uu/od/src/multifile_reader.rs

@@ -57,9 +57,10 @@ impl MultifileReader<'_> {
                     // the buffering is done elsewhere and in a way that is aware of the `-N`
                     // limit.
                     let stdin = io::stdin();
-                    #[cfg(unix)]
+                    #[cfg(any(unix, target_os = "wasi"))]
                     {
                         let stdin_raw_fd = stdin.as_raw_fd();
+                        // FIXME: unexpected close with this unsafe fd
                         let stdin_file = unsafe { File::from_raw_fd(stdin_raw_fd) };
                         self.curr_file = Some(Box::new(stdin_file));
                     }
@@ -68,7 +69,7 @@ impl MultifileReader<'_> {
                     // we don't need to prevent stdin buffering. This is sub-optimal (since
                     // there will still be additional buffering further up the stack), but
                     // doesn't seem worth worrying about at this time.
-                    #[cfg(not(unix))]
+                    #[cfg(not(any(unix, target_os = "wasi")))]
                     {
                         self.curr_file = Some(Box::new(stdin));
                     }