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

src/Mod/Import/App/CMakeLists.txt

@@ -87,6 +87,9 @@ generate_from_xml(StepShapePy)
 
 add_library(Import SHARED ${Import_SRCS})
 target_link_libraries(Import ${Import_LIBS})
+if (FREECAD_WARN_ERROR)
+    target_compile_warn_error(Import)
+endif()
 
 ADD_CUSTOM_TARGET(ImportPy ALL
     SOURCES ${SCL_Resources}

src/Mod/Import/Gui/CMakeLists.txt

@@ -39,6 +39,9 @@ SET(ImportGui_SRCS
 
 add_library(ImportGui SHARED ${ImportGui_SRCS})
 target_link_libraries(ImportGui ${ImportGui_LIBS})
+if (FREECAD_WARN_ERROR)
+    target_compile_warn_error(ImportGui)
+endif()
 
 
 SET_BIN_DIR(ImportGui ImportGui /Mod/Import)