build: do not treat deprecation warnings as errors

build-support/custom-modules/ns3-module-macros.cmake

@@ -399,7 +399,6 @@ function(build_lib)
     target_include_directories(
       ${bindings-name} PUBLIC ${Python3_INCLUDE_DIRS} ${bindings_output_folder}
     )
-    target_compile_options(${bindings-name} PRIVATE -Wno-error)
 
     # If there is any, remove the "lib" prefix of libraries (search for
     # "set(lib${BLIB_LIBNAME}")

build-support/macros-and-definitions.cmake

@@ -361,7 +361,7 @@ macro(process_options)
     else()
       add_compile_options(-Wall) # -Wextra
       if(${NS3_WARNINGS_AS_ERRORS})
-        add_compile_options(-Werror)
+        add_compile_options(-Werror -Wno-error=deprecated-declarations)
       endif()
     endif()
   endif()