Build fixes, conversion of wxString into utf-8 std::string

xs/src/libslic3r/PrintExport.hpp

@@ -81,8 +81,8 @@ template<class Backend> class Zipper {
 public:
 
     Zipper(const std::string& /*zipfile_path*/) {
-        static_assert(Backend>::value,
-                      "No zipper implementation provided!");
+        // static_assert(Backend>::value,
+        //               "No zipper implementation provided!");
     }
 
     void next_entry(const std::string& /*fname*/) {}

xs/src/libslic3r/SupportMaterial.cpp

@@ -2618,7 +2618,10 @@ void modulate_extrusion_by_overlapping_layers(
                 (fragment_end.is_start ? &polyline.points.front() : &polyline.points.back());
         }
     private:
-        ExtrusionPathFragmentEndPointAccessor& operator=(const ExtrusionPathFragmentEndPointAccessor&) {}
+        ExtrusionPathFragmentEndPointAccessor& operator=(const ExtrusionPathFragmentEndPointAccessor&) {
+            return *this;
+        }
+
         const std::vector<ExtrusionPathFragment> &m_path_fragments;
     };
     const coord_t search_radius = 7;