toaster: orm gen_layerdeps Protect against circular Layer dependencies
Limit the recursion (to say 20 levels) when processing layer dependencies
so that circular dependecies do not cause infinite decent and an
out-of-memory failure. The duplicate found layers are already immediately
filtered in the code.
[YOCTO #10630]
Signed-off-by: David Reyna <David.Reyna@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>