Due to the SONAME of `/usr/lib/libmozjs-52.so` not matching its file name, ldconfig created an untracked file `/usr/lib/libmozjs-52.so.0`. This is now fixed and both files are present in the package. To pass the upgrade, remove `/usr/lib/libmozjs-52.so.0` prior to upgrading. URL: https://www.archlinux.org/news/js52-5273-2-upgrade-requires-intervention/