boards.txt issue for 'Arduino' boards

[JAndrassy]

The existing setting of extra flags for 'Arduino' boards overrides the default from platform.txt without defining the ESP8266 flag. It is a problem for example for Blynk library. Please change them like:

arduino-esp8266.menu.BoardModel.unowifideved.build.extra_flags=-DF_CRYSTAL=40000000 -DESP8266