For other boards, I’m using makefiles which pass variables with their value to the compiler through -DVARIABLE=VALUE.
This is part of embedXcode, a template for embedded computing on Xcode.
I’d like to leverage the makefiles provided by Particle, but there’s only one option missing. Just add another variable to the make invocation as described at this page, e.g. VARIABLE_NAME=VARIABLE VARIABLE_VALUE=VALUE.