[spv-out] Multiple entry points causes failure with Adreno drivers

[encounter]

Can be reproduced with a shader as simple as:

[[stage(fragment)]]
fn fs_main_linear(in: VertexOutput) -> FragmentOutput {
    return in.v_Color;
}

[[stage(fragment)]]
fn fs_main_srgb(in: VertexOutput) -> FragmentOutput {
    return in.v_Color;
}

Vulkan failure when creating render pipeline, simply ERROR_UNKNOWN, no other information.

(Tested with Adreno 620 on Pixel 5a)