[LoongArch] `addrspacecast` missing

This error occurs when building `rust 1.72.1` on alpine:

```
LLVM ERROR: Cannot select: 0xffde112cd0: i64 = addrspacecast[1 -> 0] Constant: i64<0>
  0xffde112870: i64 = Constant<0>
In function: _ZN103_$LT$alloc..vec..into_iter..IntoIter$LT$T$C$A$GT$u20$as$u20$core..iter..traits..iterator..Iterator$GT$24__iterator_get_unchecked17h87aefb477eefd6c5E
```