Rollup merge of rust-lang#127460 - Borgerr:clarify-drop-comment, r=jhpratt

clarify `sys::unix::fd::FileDesc::drop` comment

closes rust-lang#66876

simply clarifies some resource-relevant things regarding the `close` syscall to reduce the amount of search needed in other parts of the web.

Author: matthiaskrgr

library/std/src/os/fd/owned.rs

@@ -175,6 +175,11 @@ impl Drop for OwnedFd {
             // the file descriptor was closed or not, and if we retried (for
             // something like EINTR), we might close another valid file descriptor
             // opened after we closed ours.
+            // However, this is usually justified, as some of the major Unices
+            // do make sure to always close the FD, even when `close()` is interrupted,
+            // and the scenario is rare to begin with.
+            // Helpful link to an epic discussion by POSIX workgroup:
+            // http://austingroupbugs.net/view.php?id=529
             #[cfg(not(target_os = "hermit"))]
             {
                 #[cfg(unix)]