glsl: fix clockARB builtin function

The underlying intrinsic is defined to always have a uvec2 return type.

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/compiler/glsl/builtin_functions.cpp

@@ -5947,7 +5947,7 @@ builtin_builder::_shader_clock(builtin_available_predicate avail,
 {
    MAKE_SIG(type, avail, 0);
 
-   ir_variable *retval = body.make_temp(type, "clock_retval");
+   ir_variable *retval = body.make_temp(glsl_type::uvec2_type, "clock_retval");
 
    body.emit(call(shader->symbols->get_function("__intrinsic_shader_clock"),
                   retval, sig->parameters));