WIP: Resolve "Add libretro dosbox core(s)"

Please make sure your MR is ready to be merged !

• You added the changes in CHANGELOG.md
• You described the MR as below
• You updated the recalbox wiki
• You wrote a blog post on recalbox-blog

Changes :

• Add https://github.com/libretro/dosbox-core
• ERROR: https://pastebin.com/aLiVgYgH
• https://github.com/libretro/dosbox-core/blob/libretro/libretro/Makefile.libretro

Related to :

• link other PR or issues here

Closes #1181 (closed)