cmake: disable checks for protobuf generated files

cmake/OpenCVUtils.cmake

@@ -565,6 +565,24 @@ macro(ocv_append_build_options var_prefix pkg_prefix)
   endforeach()
 endmacro()
 
+function(ocv_append_source_files_cxx_compiler_options files_var)
+  set(__flags "${ARGN}")
+  ocv_check_flag_support(CXX "${__flags}" __HAVE_COMPILER_OPTIONS_VAR "")
+  if(${__HAVE_COMPILER_OPTIONS_VAR})
+    foreach(source ${${files_var}})
+      if("${source}" MATCHES "\\.(cpp|cc|cxx)$")
+        get_source_file_property(flags "${source}" COMPILE_FLAGS)
+        if(flags)
+          set(flags "${flags} ${__flags}")
+        else()
+          set(flags "${__flags}")
+        endif()
+        set_source_files_properties("${source}" PROPERTIES COMPILE_FLAGS "${flags}")
+      endif()
+    endforeach()
+  endif()
+endfunction()
+
 # Usage is similar to CMake 'pkg_check_modules' command
 # It additionally controls HAVE_${define} and ${define}_${modname}_FOUND variables
 macro(ocv_check_modules define)

modules/dnn/CMakeLists.txt

@@ -87,6 +87,11 @@ if(WITH_INF_ENGINE AND HAVE_INF_ENGINE)
 endif()
 
 ocv_module_include_directories(${include_dirs})
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+  ocv_append_source_files_cxx_compiler_options(fw_srcs "-Wno-suggest-override")  # GCC
+elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+  ocv_append_source_files_cxx_compiler_options(fw_srcs "-Wno-inconsistent-missing-override")  # Clang
+endif()
 ocv_glob_module_sources(${sources_options} SOURCES ${fw_srcs})
 ocv_create_module(${libs})
 ocv_add_samples()