FORMUS3IC_LAS3 / embb

The old version depended on the build-dir to be a subdirectory of the
source directory.
With this patch one can build in tree or put the build-dir anywhere.

Signed-off-by: Henning Schild <henning...@siemens.com>

  (this probably works on MacOS too, but not tested yet)

While on it, fix error message. The missing include file
is not the root cause of the problem. The missing implementation
of embb_core_count_available() is.