Created attachment 217144 [details]
output from a failed make run
qt5-webengine-5.15.0_2 fails to build on 12.1-STABLE.
See the attached output of a failed make run.
Are you upgrading from an older version?
Presumably picking up an old version of the installed libraries while linking the newer ones. Best to build clean in poudriere.
This looks like it was the same cause described in bug 255007 (as suggested by comment 1 & comment 2). It definitely was linking with libQt5WebEngineCore.so from /usr/local instead of the work dir.