compiler/types: Don't duplicate empty string

We can use the static version of the empty string.  There's no worry
about freeing that string incorrectly since what is being deallocated
later is the whole mem_ctx.

Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25160>

src/compiler/glsl_types.cpp

@@ -178,7 +178,7 @@ glsl_type::glsl_type(const glsl_type *return_type,
    this->mem_ctx = ralloc_context(NULL);
    assert(this->mem_ctx != NULL);
 
-   this->name = ralloc_strdup(this->mem_ctx, "");
+   this->name = "";
 
    this->fields.parameters = rzalloc_array(this->mem_ctx,
                                            glsl_function_param, num_params + 1);