Fork of RetroArch modified to make 3DS forwarders with it.
Compile it using make -f Makefile.ctr
You'll need devkitARM_r45, aemstro, libctru_1.1_mod, and the current core you want to make a CIA of, compiled and named libretro_ctr.a on the root.
make -f Makefile.ctr -clean compiles the RomFS, so just run that before compiling.