const vectors are not removed from shaders that don't use them

[jlfwong]

The following shaders:

const vec4 someConst = vec4(3.0);

export void vertex() {
  gl_Position = vec4(0.0);
}

export void colorFragment() {
  gl_FragColor = vec4(0.0);
}

Include a constant declaration for someConst in every output shader, even though it's unused:

{
  "shaders": [
    {
      "name": "vertex",
      "contents": "const vec4 a=vec4(3.);void main(){gl_Position=vec4(0.);}"
    },
    {
      "name": "colorFragment",
      "contents": "const vec4 a=vec4(3.);void main(){gl_FragColor=vec4(0.);}"
    }
  ],
  "renaming": {}
}

The expected output in this case should be:

{
  "shaders": [
    {
      "name": "vertex",
      "contents": "void main(){gl_Position=vec4(0.);}"
    },
    {
      "name": "colorFragment",
      "contents": "void main(){gl_FragColor=vec4(0.);}"
    }
  ],
  "renaming": {}
}