build: clear 12 platform-gated warnings the x64 census could not see (#15633)

src/slic3r/GUI/InstanceCheck.hpp

@@ -87,7 +87,6 @@ private:
 	std::condition_variable m_thread_stop_condition;
 	mutable std::mutex 		m_thread_stop_mutex;
 	bool 					m_stop{ false };
-	bool					m_start{ true };
 	
 	// background thread method
 	void    listen();

src/slic3r/GUI/SelectMachinePop.hpp

@@ -183,7 +183,9 @@ private:
     HyperLink*                        m_hyperlink{nullptr}; // ORCA
     wxBoxSizer *                      m_sizer_my_devices{nullptr};
     wxBoxSizer *                      m_sizer_other_devices{nullptr};
+#if defined(__WINDOWS__)
     wxBoxSizer *                      m_sizer_search_bar{nullptr};
+#endif
     wxSearchCtrl*                     m_search_bar{nullptr};
     wxScrolledWindow *                m_scrolledWindow{nullptr};
     wxTimer *                         m_refresh_timer{nullptr};

src/slic3r/GUI/TextureImportDialog.cpp

@@ -134,7 +134,9 @@ public:
     }
 
 private:
+#if defined(__WXMSW__) || defined(__APPLE__)
     int m_suspended_count = 0;
+#endif
 };
 
 static bool needs_filament_swatch_border(const wxColour& colour)