Originally, changes to the kernel don't propagate to the other
derivation within the same package set. This commit allows for the
changes in the kernel to be propagated.
A distinct example is setting `boot.kernel.randstructSeed` to a non-zero
length string which would result in building 2 kernels, one with the
correct seed and the other with the zero length seed. Then, when using
an out-of-tree kernel driver, it would be built with the zero length
seed which differs from the non-zero length seed used to boot,
contradicting the purpose of the `boot.kernel.randstructSeed`.