libgen.h missing / undefined reference to basename() and/or dirname()

Possible reasons:
- libgen.h missing
- functions basename() and/or dirname() not available


Solution:
- drop/remove #include <libgen.h>
- implement functions basename() and/or dirname()
https://linux.die.net/man/3/dirname

or

- get latest ADE (GG/geekgadgets) from AmiNet
http://aminet.net/package/dev/gcc/ADE