With this project you are clearly using a "custom makefile" so you can't use any compiler and build stuff from within c::b.
As far as i know all changes regarding the build process (like adding libraries, or files, add defines) have to be made in the make file. Even the source tree is not take into account (so if you add a .cpp file to the project you have also to add it manually in the make file so it can be build). You have to make ALL on your own in the makefile.
With this process i can't help you. If you go with the custom makefile this is also the wrong forum to ask. You will get more help on the contiki forum. (You have to say that you are using make files, and not the c::b build process, because else they send you back to us
)
As far as i can tell the command line to the make process is called correct, as you specified, so this is no c::b bug, but how you write the TARGET variable. ( i have no idea how you have to specify it that it is right, and i also have not the time to look into it, but i can tell you that the cmd line to make is called as you write it in Project->Build Options->Make Commands)
greetings
