### Godot version

4.0b17

### System information

macOS 13.2

### Issue description

The shader function fma, used by the visual shader UVFunc node generated code:
```
// UVFunc:5
vec2 n_in5p1 = vec2(6.00000, 6.00000);
vec2 n_in5p2 = vec2(0.50000, 0.50000);
vec2 n_out5p0 = fma((UV - n_in5p2), n_in5p1, n_in5p2);
```
Does not seem to be defined in the Compatibility renderer, causing shader compilation to fail if it's used with a lot of errors and debug output (10000+ messages as it prints out a lot of engine shader code?). Ending with the relevant errors:
 ```
drivers/gles3/shader_gles3.cpp:242 - SceneShaderGLES3: Fragment shader compilation failed:
  ERROR: 0:928: Invalid call of undeclared identifier 'fma'
  ERROR: 0:930: Use of undeclared identifier 'm_n_out5p0'
  
  drivers/gles3/shader_gles3.cpp:342 - Method/function failed.
```

Simple shader using fma in Mobile:
![Screenshot 2023-02-08 at 09 52 38](https://user-images.githubusercontent.com/17763524/217483066-fe0feab7-72c4-4db7-a44e-041a1ad93f25.jpg)

Switch to Compatibility renderer:
![Screenshot 2023-02-08 at 09 53 27](https://user-images.githubusercontent.com/17763524/217483149-4fdef308-67cf-40d2-8d4a-d72dc7c85e70.jpg)



### Steps to reproduce

- Start a project in Mobile
- Make a shader where you use the fma function, for example the shader below in the reproduction field. Or a visual shader using the UVFunc node.
- Assign the shader to a shader material and apply this to a visible mesh, observe it renders
- Switch project to Compatibility renderer
- See errors and failed shader compilation

### Minimal reproduction project

Minimal test shader, use in Compatibility renderer:

```
shader_type spatial;

void fragment() {
	vec2 n_in5p1 = vec2(6.00000, 6.00000);
	vec2 n_in5p2 = vec2(0.50000, 0.50000);
	vec2 n_out5p0 = fma((UV - n_in5p2), n_in5p1, n_in5p2);

	ALBEDO = vec3(1,0,0);
}

```
error = true;
														}
													} else if (current_function != varying_function_names.fragment) { 
														error = true;
													}
													break;
												default:
													break;
											}
											if (error) {
												_set_error(vformat(RTR("Varying '%s' cannot be passed for the '%s' parameter in that context."), varname, _get_qualifier_str(arg_qual)));
												return nullptr;
											}
										}
									}
									bool is_const_arg = call_function->arguments[i].is_const;
									if (is_const_arg || is_out_arg) {
										StringName varname;
										if (n->type == Node::TYPE_CONSTANT || n->type == Node::TYPE_OPERATOR || n->type == Node::TYPE_ARRAY_CONSTRUCT) {
											if (!is_const_arg) {
												error = true;
											}
										} else if (n->type == Node::TYPE_ARRAY) {
											ArrayNode *an = static_cast<ArrayNode *>(n);
											if (!is_const_arg && (an->call_expression != nullptr || an->is_const)) {
												error = true;
											}
											varname = an->name;
										} else if (n->type == Node::TYPE_VARIABLE) {
											VariableNode *vn = static_cast<VariableNode *>(n);