### 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);
}

```
}
						if (tk.type == TK_OP_ASSIGN) {
							if (!is_constant) {
								_set_error(vformat(RTR("Global non-constant variables are not supported. Expected '%s' keyword before constant definition."), "const"));
								return ERR_PARSE_ERROR;
							}
							if (constant.array_size > 0 || unknown_size) {
								bool full_def = false;
								VariableDeclarationNode::Declaration decl;
								decl.name = name;
								decl.size = constant.array_size;
								tk = _get_token();
								if (tk.type != TK_CURLY_BRACKET_OPEN) {
									if (unknown_size) {
										_set_expected_error("{");
										return ERR_PARSE_ERROR;
									}
									full_def = true;
									DataPrecision precision2 = PRECISION_DEFAULT;
									if (is_token_precision(tk.type)) {
										precision2 = get_token_precision(tk.type);
										tk = _get_token();
										if (!is_token_nonvoid_datatype(tk.type)) {
											_set_error(RTR("Expected data type after precision modifier."));
											return ERR_PARSE_ERROR;
										}
									}
									StringName struct_name2;
									DataType type2;
									if (shader->structs.has(tk.text)) {