Update port_def.inc
Update port_def.inc

Fix for Windows build with MinGW-w64 compiler which has __has_attribute but has issues with __attribute__((weak)).
google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf