### 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
}
	HashMap<String, String>::Iterator el = gen_code.code.begin();
	while (el) {
		print_line("\n**code " + el->key + ":\n" + el->value);
		++el;
	}
	print_line("\n**uniforms:\n" + gen_code.uniforms);
	print_line("\n**vertex_globals:\n" + gen_code.stage_globals[ShaderCompiler::STAGE_VERTEX]);
	print_line("\n**fragment_globals:\n" + gen_code.stage_globals[ShaderCompiler::STAGE_FRAGMENT]);
#endif
	shader_singleton->shader.version_set_code(version, gen_code.code, gen_code.uniforms, gen_code.stage_globals[ShaderCompiler::STAGE_VERTEX], gen_code.stage_globals[ShaderCompiler::STAGE_FRAGMENT], gen_code.defines);
	ERR_FAIL_COND(!shader_singleton->shader.version_is_valid(version));
	ubo_size = gen_code.uniform_total_size;
	ubo_offsets = gen_code.uniform_offsets;
	texture_uniforms = gen_code.texture_uniforms;
	
	
	if (alpha_antialiasing_mode != ALPHA_ANTIALIASING_OFF) {
		blend_mode = BLEND_MODE_ALPHA_TO_COVERAGE;
	}
	RD::PipelineColorBlendState::Attachment blend_attachment;
	switch (blend_mode) {
		case BLEND_MODE_MIX: {
			blend_attachment.enable_blend = true;
			blend_attachment.alpha_blend_op = RD::BLEND_OP_ADD;
			blend_attachment.color_blend_op = RD::BLEND_OP_ADD;
			blend_attachment.src_color_blend_factor = RD::BLEND_FACTOR_SRC_ALPHA;
			blend_attachment.dst_color_blend_factor = RD::BLEND_FACTOR_ONE_MINUS_SRC_ALPHA;
			blend_attachment.src_alpha_blend_factor = RD::BLEND_FACTOR_ONE;
			blend_attachment.dst_alpha_blend_factor = RD::BLEND_FACTOR_ONE_MINUS_SRC_ALPHA;