src/core/slave.cpp (Slave::createSlave): Do not look for the kioslave
binary in QCoreApplication::applicationDirPath() on Q_OS_UNIX. In
distribution packages, this ends up looking for the binary in /usr/bin,
which is where the legacy kdelibs 3 installed its kioslave binary. As a
result, we end up invoking the kdelibs 3 kioslave binary with our KF5
KIO slave and crashing it due to the mixed Qt/KDE libraries.
BUG: 386859