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

src/Mod/Material/App/CMakeLists.txt

@@ -118,6 +118,9 @@ endif(FREECAD_USE_PCH)
 
 add_library(Materials SHARED ${Materials_SRCS})
 target_link_libraries(Materials ${Materials_LIBS})
+if (FREECAD_WARN_ERROR)
+    target_compile_warn_error(Materials)
+endif()
 
 SET_BIN_DIR(Materials Materials /Mod/Material)
 SET_PYTHON_PREFIX_SUFFIX(Materials)

src/Mod/Material/Gui/CMakeLists.txt

@@ -156,6 +156,9 @@ SET(MatGuiImages
 
 add_library(MatGui SHARED ${MatGui_SRCS} ${MatGuiIcon_SVG} ${MatGuiImages})
 target_link_libraries(MatGui ${MatGui_LIBS})
+if (FREECAD_WARN_ERROR)
+    target_compile_warn_error(MatGui)
+endif()
 
 SET_BIN_DIR(MatGui MatGui /Mod/Material)
 SET_PYTHON_PREFIX_SUFFIX(MatGui)