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

src/Mod/Part/App/CMakeLists.txt

@@ -582,6 +582,9 @@ endif()
 
 add_library(Part SHARED ${Part_SRCS})
 target_link_libraries(Part ${Part_LIBS})
+if (FREECAD_WARN_ERROR)
+    target_compile_warn_error(Part)
+endif()
 
 SET_BIN_DIR(Part Part /Mod/Part)
 SET_PYTHON_PREFIX_SUFFIX(Part)

src/Mod/Part/Gui/CMakeLists.txt

@@ -259,6 +259,9 @@ SET(PartGuiIcon_SVG
 
 add_library(PartGui SHARED ${PartGui_SRCS} ${PartGuiIcon_SVG})
 target_link_libraries(PartGui ${PartGui_LIBS})
+if (FREECAD_WARN_ERROR)
+    target_compile_warn_error(PartGui)
+endif()
 
 
 SET_BIN_DIR(PartGui PartGui /Mod/Part)