sstate: Implement a setscene dependency validation routine to allow skipping of some sstate installation
This is a first attempt at logic to determine when a sstate dependency needs
to be installed and when it does not. Its a start at the logic and errs on the
side of caution, as it gets wider testing, we can refine the logic as needed.
This code should allow a significant performance speedup to certain workflows, for
example "bitbake xxx-image -c rootfs" will not populate the target sysroot.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
