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_infer/src/traits/mod.rs

@@ -112,7 +112,7 @@ impl<'tcx> PolyTraitObligation<'tcx> {
 }
 
 // `PredicateObligation` 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!(PredicateObligation<'_>, 48);
 
 pub type PredicateObligations<'tcx> = Vec<PredicateObligation<'tcx>>;