Recently I had to rebuild Krita and noticed this during cmake:

-- Looking for pthread_create
-- Looking for pthread_create - not found
-- Looking for pthread_create in pthreads
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - found

Is there anything I should worry about , or does the last line mean its actually all ok?

edit: did the build (2.9.9 - git 402f4bd)- left toolbox is empty. Suggestions what's wrong greatly appreciated .

The last line means it's okay. Pthreads is needed by G'Mic only in any case. If the toolbox is really empty, your build is really messed up; but check that that it's not just that the icons are missing.

Thank you Boudewijn! You were right , it was simply a missing oxygen icon pack . And kudos for patience and letting me know about pthreads - all those messages during the build setup are a tad on a "magic" side for someone who never did it. But thx to Krita and David Revoy's excellent guide I was able to do it - and now when I set it up a 2nd time it seemed far less intimidating, even with my custom paths .