Each libretro profile records version_basis and core_version is read
there at its pin. snes9x states 1.63 in snes9x.h, nestopia 2.0.0, mgba
0.11.0, vice 3.10, atari800's libretro tree 7.0.0. Cores whose build
takes its version from git carry the nearest tag in describe form
(flycast v2.7-90-ge88b0ce, ppsspp, duckstation, gearcoleco), placeholders
copied from .info files (Git, SVN) are replaced by the code's statement,
and a code that states none is null with kind none.
Recalbox compiles uae4all from Chips-fr/uae4all-rpi (libretro-uae4all.mk:8-9), a libretro core that reads kick34005.A500 from the system directory and nothing else. built_by makes the name resolve to it on Recalbox only.
Abdessamad Derraz