Sema: preserve extern struct field alignment

In

    extern struct { x: u32, y: u16 }

we actually know that y's alignment is `@alignOf(u32)`, and not just
`@alignOf(u16)`.

closes: #16134
4620972d08Alex Kladov committed on 6/28/2023, 2:36:32 PM· committed by Jakub Konkaparent28f515a
3 files changedLine totals unavailable