Check x86_64 size assertions on aarch64, too

This makes it easier for contributors on aarch64 workstations (e.g. Macs) to
notice when these assertions have been violated.

compiler/rustc_trait_selection/src/traits/fulfill.rs

@@ -72,7 +72,7 @@ pub struct PendingPredicateObligation<'tcx> {
 }
 
 // `PendingPredicateObligation` is used a lot. Make sure it doesn't unintentionally get bigger.
-#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+#[cfg(all(any(target_arch = "x86_64", target_arch = "aarch64"), target_pointer_width = "64"))]
 static_assert_size!(PendingPredicateObligation<'_>, 72);
 
 impl<'tcx> FulfillmentContext<'tcx> {