[Migrated] Support Option<T>

Issue automatically imported from old repo: https://github.com/EmbarkStudios/rust-gpu/issues/234
Old labels: t: bug,c: rustc_codegen_spirv,s: qptr may fix
Originally creatd by fu5ha on 2020-11-12T18:04:17Z

Expected Behaviour

Be able to use Option<Mat4>

Example & Steps To Reproduce

Use an Option that contains a value larger than some threshold

    pub fn from_mat4(t: &Mat4) -> Option<Self> {
        let (scale3, rotation, translation) = t.to_scale_rotation_translation();
        if scale3.abs_diff_eq(Vec3::splat(1.0), 1e-4) {
            Some(Self::from_rotation_translation(rotation, translation))
        } else {
            None
        }
    }

Start by reproducing the reported failure with the provided Rust example and an Option value. Investigate the rustc_codegen_spirv area named by the old label; done means Option works when T exceeds the reported size threshold.