message: simplify determining size and alignment of a pointer
diff: @@ -1704,13 +1704,7 @@ pub fn eval_main<'a, 'tcx: 'a>(
  }
  // Return value
  - let ret_ptr = {
  - let ty = ecx.tcx.types.isize;
  - let layout = ecx.type_layout_with_substs(ty, Substs::empty())?;
  - let size = layout.size(&ecx.tcx.data_layout).bytes();
  - let align = layout.align(&ecx.tcx.data_layout).abi();
  - ecx.memory.allocate(size, align)?
  - };
  + let ret_ptr = ecx.memory.allocate(ecx.tcx.data_layout.pointer_size.bytes(), ecx.tcx.data_layout.pointer_align.abi())?;
  cleanup_ptr = Some(ret_ptr);
  // Push our stack frame
  