Is it possible to build the enigma2 image with two or more CPUs concurrently?
It takes quite a while to build the whole image from scratch, and it seems like a big waste to compile just one file at a time when I have a two CPU Linux box at use.

When compiling Linux for my PC, the concurrency (make -j 3) makes the compilation at least twice as fast as with no concurrency.

OK, I got that.
Following lines in "build/conf/local.conf" made the thing:

PARALLEL_MAKE = "-j 3"
BB_NUMBER_THREADS = "3"

And to make that automatic (Makefile-opendreambox overwrites it), I changed the makefile:

build/conf/local.conf:
        ...
        echo 'PARALLEL_MAKE = "-j 3"' >> build/conf/local.conf
        echo 'BB_NUMBER_THREADS = "3"' >> build/conf/local.conf

The number "3" is here the number of concurrent / parallel makes.
I'm not sure if both of these are really needed, but it doesn't hurt.