ESP8266 build.opt missing fix

[TobyChaloner]

resolves #13

[TobyChaloner]

I would have preferred to add a conditional

if ("${ARDUINO_BOARD}" MATCHES "ESP8266") 

However on the first run, when BoardOptions.cmake does not exist, the variable was empty and thereafter the CMakeCache.txt had

//Arduino board for which the project is build for
ARDUINO_BOARD:STRING=

So the variable was blank. Not sure what I am doing wrong here.

[Jookia]

I hit this issue today. What's blocking this from a merge?

[TobyChaloner]

Might be worth raising an issue on the parent repo, and reference this merge request.