In Wasm, specifying alignment of function pointers makes little sense
since function pointers are in fact indices to a Wasm table, therefore
any alignment check on those is invalid. This can cause unexpected
behaviour when checking expected alignment with `@ptrToInt(fn_ptr)`
or similar. This commit proposes to make `align` expressions a
compile error when compiled to Wasm architecture.

Some references:
[1] [Mozilla: WebAssembly Tables](https://developer.mozilla.org/en-US/docs/WebAssembly/Understanding_the_text_format#WebAssembly_tables)
[2] [Sunfishcode's Wasm Ref Manual](https://github.com/sunfishcode/wasm-reference-manual/blob/master/WebAssembly.md#indirect-call)