Will there be a package for libgccjit? I have only found one on the AUR. This will be necessary for emacs 28 with native compilation.
Until is needed by software in the official repository likely no
The emacs you are referring is
emacs-ng-git for the records
I was thinking ahead, when emacs 28 will be officially released and will be available in the Manjaro repository.
emacs-ng-git need ‘libgccjit’ also it have additional features that emacs don’t have, so there is the probability that the official emacs 28 don’t even need libgccjit