I started from the given drivers from WavGat via the AliExpress website: https://drive.google.com/open?id=10gwrG9uTDwaEO-7EudsmBkfgdcyrcABI
Install them into the created user extension folder for the Arduino IDE. On windows, normally in Documents\Arduino
When trying to compile the basic sketch about the blinking led, the compiler did give me a warning:
'Arduino AVR Boards' contains deprecated recipe.ar.pattern="{compiler.path}{compiler.ar.cmd}" {compiler.ar.flags} {compiler.ar.extra_flags} "{build.path}/{archive_file}" "{object_file}", automatically converted to recipe.ar.pattern="{compiler.path}{compiler.ar.cmd}" {compiler.ar.flags} {compiler.ar.extra_flags} "{archive_file_path}" "{object_file}".
This is caused because these given drivers are not updated regurarly to follow new developments in the Arduino IDE source code.
Second, when trying to compile the latest MySensors library (v2.3.1), I got a whole bunch of strange compile errors.
So I adapted the platform.txt to follow the normal Arduino IDE platform.txt source code. At the same time I adapted the name from 'Arduino AVR Boards' to 'WavGat AVR Boards' to distinguish them more clearly.
I added also a missing new define 'void yield(void)' in the core Arduino.h file and the missing hook.c file. (All credits and thanks to: digistump/DigistumpArduino#45)
After these changes my sketches for MySensors did compile without any errors.
In this distribution the hardware folder WAV8F is not included, it is only for the Arduino IDE 1.x version!
As the Arduino IDE will evolve in the future, other needs to change these WavGat drivers will appear. It's a bit sad that WavGat doesn't keep its software up to date!
UPDATE
Be aware that big arduino sketches with external libraries will not compile, despite my changes. Simple sketches will compile, for example the led blinking sketch will work, but when you want something more like for example extend the arduino hardware with a ehternet shield and then try to use it, good luck :-(. You will get a bunch of compile errors. Not being a compiler specialist, I gave up on my 2 euro WAVGAT board and bought a new, also 2 euro, Arduino compatible board... Maybe in the future, I hope that WAVGAT will invest more in his software drivers, because the hardware is useless without good software support!