The deleted files were all links to the master file - as I detected now.
Like Unix symbolic links? Strange. Here they are just copied.
Hmmm ... did you try to "Clean up and Build" the Lazarus project (lazarus.lpi) itself?
It does not work. It is not a "normal" project and can be used just for debugging the IDE.
Lazarus must be rebuilt from Tools -> Configure "Build Lazarus" window.