Revert use of map_or, restoring compatibility with pre-1.41 rustc

src/fcntl.rs

@@ -215,7 +215,8 @@ fn inner_readlink<P: ?Sized + NixPath>(dirfd: Option<RawFd>, path: &P)
     }
     // Uh oh, the result is too long...
     // Let's try to ask lstat how many bytes to allocate.
-    let reported_size = super::sys::stat::lstat(path).map_or(0, |x| x.st_size);
+    let reported_size = super::sys::stat::lstat(path)
+        .and_then(|x| Ok(x.st_size)).unwrap_or(0);
     let mut try_size = if reported_size > 0 {
         // Note: even if `lstat`'s apparently valid answer turns out to be
         // wrong, we will still read the full symlink no matter what.