Rollup merge of #94043 - DrMeepster:box_alloc_ice, r=oli-obk

Fix ICE when using Box<T, A> with pointer sized A

Fixes #78459

Note that using `Box<T, A>` with a more than pointer sized `A` or using a pointer sized `A` with a Box of a DST will produce a different ICE (#92054) which is not fixed by this PR.

src/test/ui/box/issue-78459-ice.rs

@@ -0,0 +1,6 @@
+// check-pass
+#![feature(allocator_api)]
+
+fn main() {
+    Box::new_in((), &std::alloc::Global);
+}