I for the 3.0 branch you can use the latest stable arduino package. Add the following link in the board manager url box in the arduino ide settings. Then install the latest stable build using the board manager.
http://arduino.esp8266.com/stable/packa ... index.json
When you download the source code from git hub copy the contents of the libraries folder to the libraries directory for your arduino environment. Under windows this will be
C:\Users\Your user name\Documents\Arduino\libraries
Now change your arduino environment to target esp8266 node mcu if you have that board otherwise use generic esp8266 and select your flash size.
You should be able to build now.
http://esp8266basic.com
A BASIC interpreter for your ESP
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