Thanks a lot for quick reply, I've included the patch in Fedora package: https://src.fedoraproject.org/rpms/mozjs78/c/15ae20d569f6d11894a1e2fc29169d10432dfb6a?branch=rawhide . However, fun doesn't end here, it seems something has changed in between mozjs78.6 and mozjs78.8:
./../../source/scriptinterface/ScriptContext.cpp: In member function 'void ScriptContext::UnRegisterRealm(JS::Realm*)':
../../../source/scriptinterface/ScriptContext.cpp:136:46: error: cannot convert 'JS::Zone*' to 'JSContext*'
136 | JS::PrepareZoneForGC(js::GetRealmZone(realm));