But I already have plib 1.8.5 installed, I can build and run flightgear, otherwise it would be impossible to build it without plib.
I already have simgear 1.9.1 installed.
Can it be a version mismatch? Maybe another version of plib is required for building it?
Or maybe i have to give it a special path for plib libraries. Although it can see plib/pu.h while checking for plib dependency in configure step, not being able to find plib/sg.h of it is really weird. (I manually checked and saw that there is a sg.h file in /usr/include/plib directory and it's not an empty file.)