How to create a #define across the complete project

[Dave McLaughlin]

I have 2 builds that have different settings. Most of the settings can be handled in the device/yourplatform folder but I also want to make changes to the AOSP source and compile the code based on this define.

Is it possible to set a define in one of the .mk files and somehow use this to across the project and have compile time code selection?

Hope that makes sense?