NetBSD: Implement OS_Unix::get_executable_path()
NetBSD: Implement OS_Unix::get_executable_path()

Same implementation as OpenBSD seems to work fine.

(cherry picked from commit 01185acecbdfc95b1b9421dac32ee64705108a4b)

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot