meta/lib/oe/copy_buildsystem.py: do not derefence symlinks

meta/lib/oe/copy_buildsystem.py: do not derefence symlinks

This was added (I think) for the purpose of supporting layers that refer
to items outside of the layer via relative symlinks:
https://git.yoctoproject.org/poky-contrib/commit/?id=d31d1ad4e566e42d0bbcf1f41ac25e33181fb517

I do not think copying the link target into the layer that references it is the
correct solution: rather the original target should be included
into the SDK with the same relative path.

This change is done for the sake of preserving symlinks
that are referencing things inside the layer as they are;
particularly the content of scripts/esdk-tools/.

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>