Revert "third_party/protobuf: Update to HEAD (83d681ee2c)"

third_party/protobuf/cmake/libprotoc.cmake

 set(libprotoc_files
   ${protobuf_source_dir}/src/google/protobuf/compiler/code_generator.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/command_line_interface.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/cpp/cpp_enum.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/cpp/cpp_enum_field.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/cpp/cpp_extension.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/cpp/cpp_field.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/cpp/cpp_file.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/cpp/cpp_generator.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/cpp/cpp_helpers.cc
@@ skipping 54 matching lines @@
   ${protobuf_source_dir}/src/google/protobuf/compiler/javanano/javanano_extension.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/javanano/javanano_field.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/javanano/javanano_file.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/javanano/javanano_generator.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/javanano/javanano_helpers.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/javanano/javanano_map_field.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/javanano/javanano_message.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/javanano/javanano_message_field.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/javanano/javanano_primitive_field.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/js/js_generator.cc
-  ${protobuf_source_dir}/src/google/protobuf/compiler/js/well_known_types_embed.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/objectivec/objectivec_enum.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/objectivec/objectivec_enum_field.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/objectivec/objectivec_extension.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/objectivec/objectivec_field.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/objectivec/objectivec_file.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/objectivec/objectivec_generator.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/objectivec/objectivec_helpers.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/objectivec/objectivec_map_field.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/objectivec/objectivec_message.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/objectivec/objectivec_message_field.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/objectivec/objectivec_oneof.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/objectivec/objectivec_primitive_field.cc
-  ${protobuf_source_dir}/src/google/protobuf/compiler/php/php_generator.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/plugin.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/plugin.pb.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/python/python_generator.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/ruby/ruby_generator.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/subprocess.cc
   ${protobuf_source_dir}/src/google/protobuf/compiler/zip_writer.cc
 )
 
 add_library(libprotoc ${protobuf_SHARED_OR_STATIC}
   ${libprotoc_files})
 target_link_libraries(libprotoc libprotobuf)
 if(MSVC AND protobuf_BUILD_SHARED_LIBS)
   target_compile_definitions(libprotoc
     PUBLIC  PROTOBUF_USE_DLLS
     PRIVATE LIBPROTOC_EXPORTS)
 endif()
 set_target_properties(libprotoc PROPERTIES
     COMPILE_DEFINITIONS LIBPROTOC_EXPORTS
     OUTPUT_NAME ${LIB_PREFIX}protoc
     DEBUG_POSTFIX "${protobuf_DEBUG_POSTFIX}")