CMake 2.8.12 and lower allowed the SOURCE signature in add_custom_command

In CMake 3.0 the policy CMP0050 was introduced where it could be set to OLD to keep this behaviour while for NEW an error was raised.
Since CMake 3.5.2 a warning comes up when using the OLD behaviour and that it will be removed in a future version.

In FreeCAD we switched to the new behaviour now and removed the SOURCE signature from add_custom_command which affects the macros
fc_copy_sources, fc_target_copy_resource and fc_target_copy_resource_flat and their usage.
It's not possible any more to add files to a target by using the macros. Now a file must be added to the target before using the macros.

This commit fixes it for Arch, Draft, OpenSCAD, Material, Plot and Ship

src/Mod/Plot/CMakeLists.txt

@@ -52,12 +52,18 @@ SOURCE_GROUP("plotutils" FILES ${PlotUtils_SRCS})
 
 SET(all_files ${PlotMain_SRCS} ${PlotAxes_SRCS} ${PlotLabels_SRCS} ${PlotPositions_SRCS} ${PlotSave_SRCS} ${PlotSeries_SRCS} ${PlotUtils_SRCS})
 
+SET(PlotGuiIcon_SVG
+    resources/icons/PlotWorkbench.svg
+)
+
 ADD_CUSTOM_TARGET(Plot ALL
-    SOURCES ${all_files} ${Plot_QRC_SRCS}
+    SOURCES ${all_files} ${Plot_QRC_SRCS} ${PlotGuiIcon_SVG}
 )
 
 fc_copy_sources(Plot "${CMAKE_BINARY_DIR}/Mod/Plot" ${all_files})
 
+fc_copy_sources(Plot "${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_DATADIR}/Mod/Plot" ${PlotGuiIcon_SVG})
+
 IF (BUILD_GUI)
     fc_target_copy_resource(Plot
         ${CMAKE_CURRENT_BINARY_DIR}
@@ -108,11 +114,9 @@ INSTALL(
     DESTINATION
         Mod/Plot
 )
-
-SET(PlotGuiIcon_SVG
-    resources/icons/PlotWorkbench.svg
+INSTALL(
+    FILES
+        ${PlotGuiIcon_SVG}
+    DESTINATION
+        "${CMAKE_INSTALL_DATADIR}/Mod/Plot/resources/icons"
 )
-
-fc_copy_sources(Plot "${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_DATADIR}/Mod/Plot" ${PlotGuiIcon_SVG})
-
-INSTALL(FILES ${PlotGuiIcon_SVG} DESTINATION "${CMAKE_INSTALL_DATADIR}/Mod/Plot/resources/icons")