If you accidentally create symlinks in the glibc sources directory, it
fails in very hard to understand ways. Whilst most people don't do this,
since I debugged it, specifify the list of plugins we use to avoid
this biting anyone else.
(From OE-Core rev: 38a1d4ae4df8dd21546b7442e5a3bddca32a4734)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>