Can not get struct member addresses at compile time

[jfondren]

On Wednesday, 16 June 2021 at 11:56:31 UTC, Mike Parker wrote:
> https://dlang.org/spec/pragma.html#crtctor
"as a simple replacement for shared static this in betterC mode"

Cool.

However,

```d
immutable int example;

version(D_BetterC) {
     pragma(crt_constructor) extern(C) void initialize() {
         example = 1;
     }
} else {
     shared static this() {
         example = 1;
     }
}
```

this compiles without -betterC; with -betterC it errors out:

Error: cannot modify `immutable` expression `example`

Is this a bug?