- All compilers used support the -I option for setting an include search directory.
- The Contiki source tree follows the (common) approach of placing declarations (in headerf iles) in the same directory as definitions (in source files).
As a result it makes sense to use the -I compiler option for just the same set of directories used for the vpath gnumake directive.
Note: I checked several builds but nevertheless one or the other might need some additional adjustsments. Sorry for the inconvenience.