FIX: incorrect print sequence of support filament on first layer

jira: none
Change-Id: I893fc773849a5557c138de3f9bd1c3ec1e1978df
(cherry picked from commit 3b988f6b77d2375b98f30727a8d72a4524970f62)

src/libslic3r/GCode.cpp

@@ -2472,6 +2472,9 @@ void GCode::_do_export(Print& print, GCodeOutputStream &file, ThumbnailsGenerato
     if (!machine_start_gcode.empty() && this->m_fan_mover.get() != nullptr)
         file.write(this->m_fan_mover.get()->process_gcode("", true));
 
+    // init extrude
+    m_writer.init_extruder(initial_non_support_extruder_id);
+
     // Process filament-specific gcode.
    /* if (has_wipe_tower) {
         // Wipe tower will control the extruder switching, it will call the filament_start_gcode.
@@ -6466,9 +6469,6 @@ std::string GCode::retract(bool toolchange, bool is_last_retraction, LiftType li
 
 std::string GCode::set_extruder(unsigned int new_filament_id, double print_z, bool by_object)
 {
-    //init extrude
-    m_writer.init_extruder(new_filament_id);
-
     int new_extruder_id = get_extruder_id(new_filament_id);
     if (!m_writer.need_toolchange(new_filament_id))
         return "";