Along with `/usr/$(get_libdir)/swift-${PV}`, symlink to a stable
directory in `/usr/$(get_libdir)` that matches the package SLOT so
revdeps can rely on a stable directory that doesn't change on patch
version.
Closes: https://bugs.gentoo.org/957730
Signed-off-by: Itai Ferber <itai@itaiferber.net>
