指令：
flutter --android-sdk "[路徑]
範例：
C:\Users\danny>flutter config --android-sdk "D:\3106_AndroidSDK"
Setting "android-sdk" value to "D:\3106_AndroidSDK".
You may need to restart any open editors for them to read new settings.
記得指定完成後執行flutter doctor --android-licenses 去同意整個授權才能使用！