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

src/Mod/Test/Gui/CMakeLists.txt

@@ -61,6 +61,9 @@ add_library(QtUnitGui SHARED ${TestGui_SRCS} ${TestGuiPy_SRCS} ${TestGuiIcon_SVG
 
 target_link_libraries(QtUnitGui ${TestGui_LIBS})
 add_dependencies(QtUnitGui Test)
+if (FREECAD_WARN_ERROR)
+    target_compile_warn_error(QtUnitGui)
+endif()
 
 fc_copy_sources(QtUnitGui "${CMAKE_BINARY_DIR}/Mod/Test" qtunittest.py)
 fc_copy_sources(QtUnitGui "${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_DATADIR}/Mod/Test" ${TestGuiIcon_SVG})