Compile Cocoa control example in Unix "widgets" sample makefile

Previously this was never done, as we couldn't determine if we were
using Cocoa or not at generation time, but we can determine it in the
makefile itself.

samples/widgets/makefile.unx

@@ -220,5 +220,14 @@ widgets_widgets.o: ./widgets.cpp
 .PHONY: all install uninstall clean
 
 
+widgets_native_wrapper.o: ./native_wrapper.mm ./native.cpp
+	$(CXX) -c -o $@ $(WIDGETS_CXXFLAGS) $(OBJCXXFLAGS) ./native_wrapper.mm
+
+ifeq ($(WX_PORT),osx_cocoa)
+WIDGETS_OBJECTS += widgets_native_wrapper.o
+
+widgets: widgets_native_wrapper.o
+endif
+
 # Dependencies tracking:
 -include ./*.d

samples/widgets/widgets.bkl

@@ -13,13 +13,27 @@
       -->
     <set var="NATIVE_OBJCPP_SRC">
         <if cond="OUT_OF_TREE_MAKEFILES=='1'">
-            <!-- We can't determine if we're using Cocoa or not, assume we don't -->
+            <!--
+                We can't determine if we're using Cocoa or not at generation
+                time, so deal with it in the makefile fragment below.
+             -->
         </if>
         <if cond="TOOLKIT=='OSX_COCOA' and WXUNIV=='0'">
             native_wrapper.mm
         </if>
     </set>
 
+    <fragment format="gnu">
+widgets_native_wrapper.o: ./native_wrapper.mm ./native.cpp
+	$(CXX) -c -o $@ $(WIDGETS_CXXFLAGS) $(OBJCXXFLAGS) ./native_wrapper.mm
+
+ifeq ($(WX_PORT),osx_cocoa)
+WIDGETS_OBJECTS += widgets_native_wrapper.o
+
+widgets: widgets_native_wrapper.o
+endif
+    </fragment>
+
     <exe id="widgets" template="wx_sample" template_append="wx_append">
         <sources>
             activityindicator.cpp