the unit "Infodwrf" is for heaptrc.
It is used (compiled into your exe) if you specify -gh and -gw
gh heaptrace
gw dwarf
Infodwrf prints a backtrace to console, if your app crashes. It does that from inside your app, it needs no gdb for that.
If you want to debug in gdb (or in Lazarus, which does use gdb by default) then -gh is not needed. You only need -gw (and maybe -godwarfsets )
I have no idea why you could not find it in your fpc.