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

src/Mod/Assembly/App/CMakeLists.txt

@@ -52,6 +52,9 @@ SET(Assembly_SRCS
 
 add_library(Assembly SHARED ${Assembly_SRCS})
 target_link_libraries(Assembly ${Assembly_LIBS})
+if (FREECAD_WARN_ERROR)
+    target_compile_warn_error(Assembly)
+endif()
 
 if(FREECAD_USE_PCH)
     add_definitions(-D_PreComp_)

src/Mod/Assembly/Gui/CMakeLists.txt

@@ -67,6 +67,9 @@ SET(AssemblyGuiIcon_SVG
 
 add_library(AssemblyGui SHARED ${AssemblyGui_SRCS} ${AssemblyGuiIcon_SVG})
 target_link_libraries(AssemblyGui ${AssemblyGui_LIBS})
+if (FREECAD_WARN_ERROR)
+    target_compile_warn_error(AssemblyGui)
+endif()
 
 SET_BIN_DIR(AssemblyGui AssemblyGui /Mod/Assembly)
 SET_PYTHON_PREFIX_SUFFIX(AssemblyGui)