what happens when you just use the compiler like this:
fpc -Tlinux helloworld.pas
But then again, an install from the apt repository indeed draws in buildessential as a dependency as well as several other -dev packages that you otherwise need to install by hand.
I suggest you follow my path: install 2.6.2 , build 3.0.2 compiler only, use that to bootstrap the higher versions. Slightly more work, but worked for me on a second system too.
I tested that this morning.
Also note: is there an fpc.cfg in the way? Check for one in /etc/fpc.cfg