### Godot version

4.0.2.stable

### System information

Windows 11, Vulkan, RTX2070 Super

### Issue description

Reading from `VIEWPORT_SIZE` in the `light()` function causes spatial shader to break and renders as default white.

### Steps to reproduce

![image](https://user-images.githubusercontent.com/20043270/236914345-ccd12e83-4431-4a53-b67b-028c8ef5719b.png)

when line 51 is present the fails to compile with the following message in the output log but no compilation errors.

```
servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.cpp:171 - Condition "!shader_singleton->shader.version_is_valid(version)" is true.
  drivers/vulkan/rendering_device_vulkan.cpp:5361 - Condition "!shader" is true. Returning: RID()
  drivers/vulkan/rendering_device_vulkan.cpp:5835 - Condition "!us" is true.
```

commenting out line 51 solves this issue.

[The documentation](https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/spatial_shader.html#light-built-ins) states that `VIEWPORT_SIZE` should be available to the `light()` function.

### Minimal reproduction project

N/A
uses_transmittance = false;
	uses_time = false;
	writes_modelview_or_projection = false;
	uses_world_coordinates = false;
	uses_particle_trails = false;
	int depth_drawi = DEPTH_DRAW_OPAQUE;
	ShaderCompiler::IdentifierActions actions;
	actions.entry_point_stages["vertex"] = ShaderCompiler::STAGE_VERTEX;
	actions.entry_point_stages["fragment"] = ShaderCompiler::STAGE_FRAGMENT;
	actions.entry_point_stages["light"] = ShaderCompiler::STAGE_FRAGMENT;
	actions.render_mode_values["blend_add"] = Pair<int *, int>(&blend_mode, BLEND_MODE_ADD);
	actions.render_mode_values["blend_mix"] = Pair<int *, int>(&blend_mode, BLEND_MODE_MIX);
	actions.render_mode_values["blend_sub"] = Pair<int *, int>(&blend_mode, BLEND_MODE_SUB);
	actions.render_mode_values["blend_mul"] = Pair<int *, int>(&blend_mode, BLEND_MODE_MUL);
	actions.render_mode_values["alpha_to_coverage"] = Pair<int *, int>(&alpha_antialiasing_mode, ALPHA_ANTIALIASING_ALPHA_TO_COVERAGE);
	actions.render_mode_values["alpha_to_coverage_and_one"] = Pair<int *, int>(&alpha_antialiasing_mode, ALPHA_ANTIALIASING_ALPHA_TO_COVERAGE_AND_TO_ONE);
	actions.render_mode_values["depth_draw_never"] = Pair<int *, int>(&depth_drawi, DEPTH_DRAW_DISABLED);
	actions.render_mode_values["depth_draw_opaque"] = Pair<int *, int>(&depth_drawi, DEPTH_DRAW_OPAQUE);
	actions.render_mode_values["depth_draw_always"] = Pair<int *, int>(&depth_drawi, DEPTH_DRAW_ALWAYS);
	actions.render_mode_values["depth_test_disabled"] = Pair<int *, int>(&depth_testi, DEPTH_TEST_DISABLED);
	actions.render_mode_values["cull_disabled"] = Pair<int *, int>(&cull_modei, CULL_DISABLED);
	actions.render_mode_values["cull_front"] = Pair<int *, int>(&cull_modei, CULL_FRONT);
	actions.render_mode_values["cull_back"] = Pair<int *, int>(&cull_modei, CULL_BACK);
	actions.render_mode_flags["unshaded"] = &unshaded;
	actions.render_mode_flags["wireframe"] = &wireframe;
	actions.render_mode_flags["particle_trails"] = &uses_particle_trails;
	actions.usage_flag_pointers["ALPHA"] = &uses_alpha;
	actions.usage_flag_pointers["ALPHA_SCISSOR_THRESHOLD"] = &uses_alpha_clip;
	actions.usage_flag_pointers["ALPHA_HASH_SCALE"] = &uses_alpha_clip;
	actions.usage_flag_pointers["ALPHA_ANTIALIASING_EDGE"] = &uses_alpha_antialiasing;