Avoid the -Os option when generating WebAssembly

[lukaszcz]

With -Os ill-typed code is generated for the following:

module wasmcrash.juvix;

import Stdlib.Prelude open;

{-# inline: false #-}
I {A} (x : A) : A := x;

{-# inline: false #-}
I' {A} (x : A) : A := x;

main : Nat := I' (I I 1);

Running the generated WASM file with wasmer or wasmtime gives an error:

Validation error: type mismatch: expected i32 but nothing on stack (at offset 740)

The issue occurs with clang version 16.0.5 but not 16.0.0. The issue does not occur with any other optimization option (-O1, -O2, -O3). There is no issue with -Os used with the native target.

This is thus likely a bug in a specific version of LLVM. It could be theoretically some very subtle non-conformance to the C standard in our generated code, but this seems less likely. Creating a minimum C file exposing the bug would be very time-consuming, so I propose to just avoid using the -Os option for now.