This should be more robust in future: we SHA256 all of the deps.
For wiregen we prefix with EXPERIMENTAL_FEATURES, since it can effect them.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
My node tried to rebuild one of them because it was lagging (I noticed
because mrkd was not installed).
Turns out a few were lagging, and lightning-dev-sendcustommsg.7 was totally
empty!
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>