Is there a way to read real-time port selection on Arduino IDE when using third-party toolchain and uploading program?
After someone from Github gave me a link, I think I ve found the way to read the real-time port selection even using third party uploading program.

The key is command line argument in the "Platform.txt" file located under "arduino15" folder. If you have the same issue as mine, try look up this link, where you will find loads of useful information:
https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5-3rd-party-Hardware-specification

PS: rmb, after you change the command lines in the txt file, always close and restart your arduino IDE before those changes you made take effect.