[oe] Global defines

[E Robertson]

HI All,
I'm trying to add a header file to the staging area and define some global 
variables so that this header file can be use accordingly.
Is it possible to define these global defines in a conf file so that they can 
act an env variables? How can I do this or is their an example of this?
What conf file can be used for this?
My intention is to use a package bb file to do_stage adding the custom header 
files, then add the defines to a conf file, maybe the distro conf?

Thanks.