yocto-compat-layer.py: Fix the signature validation
The initial signatures need to be collected -after- the dependency layers have
been added to the system. Otherwise changes that happen due to dependencies,
outside of the layer being scanned, will show up as signature problems.
The add_layer function was split into two pieces so that we can process
the dependencies first, and then add the layer itself for the comparison.
Signed-off-by: Mark Hatle <mark.hatle@windriver.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
