[oe] Images no longer automatically include libstdc++6

[Steve Sakoman]

Using current top of tree to build some of my images I noticed that
quite a few apps seems to be broken at run time (Firefox, Epiphany,
Gnome-mplayer, and others).

All were complaining about libstdc++6 being missing.  Manually
installing the libstdc++6 package fixed the issue.

Any idea what changed that introduced this issue?

Steve