The package for ningle has a custom phase changing the name of the
compiled files, this is why when you try to load it ASDF thinks that the
system has not been compiled yet, tries to compile it and fails because
it can't write the compiled files to the read-only "/gnu/store/...".

I don't know if this custom phase is necessary or if it's just
a leftover from the way asdf-build-system worked in the past...

Could you try the attached patch removing the custom phase and see if
everything works fine? If yes I'll push it to master.