Hi all, I've finally managed to have a pcsx_rearmed_libretro_ctr.a (with a help from libretro docs).
Prerequisite: you've downloaded and installed devkitpro, devkitARM and whatever until point 5 and you'll be using the MSYS bash bundled with it. I recommend to use the one bundled and to not download another one.
Follow the instructions until point 4, point 5 will be is as follows:
5a. If on Windows, follow the instructions to set up the environment
here (only the section Environment Configuration);
5b. Then, here follow ONLY (for now) the
fetching cores section. If you want, you may fetch only pcsx_rearmed core (as described in line
Fetch one core, with a command like:
./libretro-fetch.sh pcsx_rearmed);
5c. Now create a .sh file (name it as you want, mine is called libretro-3ds-SetEnv.sh) in the "libretro-super" folder get in point 5b and inside use the content of
this. The CTRBANNERTOOL property is not necessary and I've deleted it, you may want to let it stay there.
IMPORTANT: update the paths of devkit folders in proper way (remember, the path will start witch /c/ in unix-like shell)
Follow instructions 6-7 (I had only to modify the first row, I couldn't find the second)
8a. in MSys2 launch the .sh created in 5c
NOTE: I've used the libretro-super method with ctr and worked flawlessly. I've used the command $ ./libretro-build-ctr.sh . Although it will try to compile every core, if you followed the previous steps it will find and compile only the pcsx-rearmed core.
8c. Grab the pcsx_rearmed_libretro_ctr.a in libretro-super/dist/ctr
Now you can rename the file as described in point 7 and go on.