I tried to do exactly as your 'hello' application to see if I could compile and link.
Among some other output, I got this message on 'make O=obj_path':
Library dependencies missing: stdlibs in directory '/home/incal/core/l4re-snapshot-2013123021/src/l4/pkg/hi/server/src'; aborting.
Cflags dependencies missing: stdlibs in directory '/home/incal/core/l4re-snapshot-2013123021/src/l4/pkg/hi/server/src'; aborting. Stop.
Before I did that, it told me to 'make O=obj_path config' from src/l4, which I did, though I didn't setup anything explicitly. I had to fetch 'pkg-config' from the repos, but that worked great, only it wouldn't work less the terminal had at least 80 columns - turns out, in the Linux VT, I have 73 columns (i.e., char width), and in X, in urxvt 78. But xterm was configurable in .Xresources like this:
xterm*geometry: 80x28
Just sayin'.
What is "stdlibs"? It sounds like the C standard library except for the trailing "s".
I tried to remove the "include" stuff from the C source, as well as the 'puts' and 'sleep' (to just make it return 0) - this, I thought, would make it independent of any library routines, however, I got the same error message.