clang/gcc: Add build option FREECAD_WARN_ERROR to force to make warnings into errors

src/Mod/TechDraw/App/CMakeLists.txt

@@ -277,6 +277,9 @@ endif(FREECAD_USE_PCH)
 add_library(TechDraw SHARED ${TechDraw_SRCS} ${Draw_SRCS} ${TechDrawAlgos_SRCS}
                            ${Geometry_SRCS} ${Python_SRCS})
 target_link_libraries(TechDraw ${TechDrawLIBS} ${TechDraw})
+if (FREECAD_WARN_ERROR)
+    target_compile_warn_error(TechDraw)
+endif()
 
 ADD_CUSTOM_COMMAND(TARGET TechDraw
                    POST_BUILD

src/Mod/TechDraw/Gui/CMakeLists.txt

@@ -479,6 +479,9 @@ endif(FREECAD_USE_PCH)
 add_library(TechDrawGui SHARED ${TechDrawGui_SRCS} ${TechDrawGuiView_SRCS} ${TechDrawGuiViewProvider_SRCS}
                                ${TechDrawGuiNav_SRCS} ${TechDrawGuiIcon_SVG} ${TechDrawGuiFonts} ${MRTE_SRCS})
 target_link_libraries(TechDrawGui ${TechDrawGui_LIBS})
+if (FREECAD_WARN_ERROR)
+    target_compile_warn_error(TechDrawGui)
+endif()
 
 fc_copy_sources(TechDrawGui "${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_DATADIR}/Mod/TechDraw/" ${TechDrawGuiIcon_SVG})
 INSTALL(FILES ${TechDrawGuiIcon_SVG} DESTINATION "${CMAKE_INSTALL_DATADIR}/Mod/TechDraw/Resources/icons")