more comment

src/libpanic_unwind/lib.rs

@@ -40,6 +40,7 @@
         #[path = "miri.rs"]
         mod imp;
         // On MSVC we need the SEH lang items as well...
+        // This should match the conditions of the `seh.rs` import below.
         #[cfg(all(target_env = "msvc", not(target_arch = "aarch64")))]
         #[allow(unused)]
         mod seh;