### 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);
}

```
FunctionNode *parent_function = nullptr;
					{
						BlockNode *block = p_block;
						while (block && !block->parent_function) {
							block = block->parent_block;
						}
						parent_function = block->parent_function;
					}
					if (parent_function) {
						StringName func_name = parent_function->name;
						if (!used_local_vars.has(func_name)) {
							used_local_vars.insert(func_name, HashMap<StringName, Usage>());
						}
						used_local_vars[func_name].insert(name, Usage(tk_line));
					}
				}
#endif 
				is_const_decl = is_const;
				BlockNode::Variable var;
				var.type = type;
				var.precision = precision;
				var.line = tk_line;
				var.array_size = array_size;
				var.is_const = is_const;
				var.struct_name = struct_name;
				tk = _get_token();
				if (tk.type == TK_BRACKET_OPEN) {
					Error error = _parse_array_size(p_block, p_function_info, false, &decl.size_expression, &var.array_size, &unknown_size);
					if (error != OK) {
						return error;