Normal maps don't work with Forward rendering

### TL;TR

Normal maps don't work with Forward rendering.

### Node tree example


### Errors

```
ERROR: D:\Blender\Projects\RP\0_Build_Files\Mine\A3D\Mobile_Test\build_A3D_Mobile_Test\compiled\Shaders\Material_mesh.frag.glsl:24: 'n' : undeclared identifier
ERROR: D:\Blender\Projects\RP\0_Build_Files\Mine\A3D\Mobile_Test\build_A3D_Mobile_Test\compiled\Shaders\Material_mesh.frag.glsl:24: '' : compilation terminated
ERROR: 2 compilation errors. No code generated.
```

### Resources

Variable `n` defined here:
Assignment attempts for the undefined `n` variable:

Start by reading blender/arm/make_world.py around the definition of n and blender/arm/material/cycles.py around lines 402-408, then reproduce the reported normal-map node tree with Forward rendering. Check the generated Material_mesh.frag.glsl for the undefined variable and confirm that the shader compiles and normal maps work when the issue is resolved.

Written by the indexing model from the issue text.