### 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);
}

```
}
			String return_struct_name = String(b->parent_function->return_struct_name);
			String array_size_string;
			if (b->parent_function->return_array_size > 0) {
				array_size_string = "[" + itos(b->parent_function->return_array_size) + "]";
			}
			ControlFlowNode *flow = alloc_node<ControlFlowNode>();
			flow->flow_op = FLOW_OP_RETURN;
			pos = _get_tkpos();
			tk = _get_token();
			if (tk.type == TK_SEMICOLON) {
				
				if (b->parent_function->return_type != TYPE_VOID) {
					_set_error(vformat(RTR("Expected '%s' with an expression of type '%s'."), "return", (!return_struct_name.is_empty() ? return_struct_name : get_datatype_name(b->parent_function->return_type)) + array_size_string));
					return ERR_PARSE_ERROR;
				}
			} else {
				_set_tkpos(pos); 
#ifdef DEBUG_ENABLED
				if (b->parent_function->return_type == DataType::TYPE_BOOL) {
					keyword_completion_context = CF_BOOLEAN;
				}
#endif 
				Node *expr = _parse_and_reduce_expression(p_block, p_function_info);
				if (!expr) {
					return ERR_PARSE_ERROR;
				}
				if (b->parent_function->return_type != expr->get_datatype() || b->parent_function->return_array_size != expr->get_array_size() || return_struct_name != expr->get_datatype_name()) {
					_set_error(vformat(RTR("Expected return with an expression of type '%s'."), (!return_struct_name.is_empty() ? return_struct_name : get_datatype_name(b->parent_function->return_type)) + array_size_string));
					return ERR_PARSE_ERROR;