Howto Compile fltk Hello World Example

This took me much longer than I expected, because there is no pkg-config for fltk, but a separate program which generates a compile command.

fltk-config --cxx --cxxflags --use-cairo --compile hello.cxx

and there are required packages:

apt-get install libcairo2-dev build-essential g++

maybe there is more of them.