There is a bundled copy of mozjpeg here: package-cache/v6/npm-mozjpeg-8.0.0-cd990d96581626ca64b877146ce22ba00b3b308c-integrity/node_modules/mozjpeg/vendor/source/mozjpeg.tar.gz It's from 2017, so it lacks quite a few security fixes. Newer mozjpeg releases also fix a C99 compatibility issue in the right-shift-is-signed check (implicit declaration of the exit function).
Done in pgadmin4-6.18-1.fc38.
Thanks, fix verified.