dev_override_randbytes() hashes argv0 into the CLN_DEV_ENTROPY_SEED
stream, so every plugin and subdaemon gets a distinct seed. But
lightningd execs them with absolute paths, so the "deterministic"
stream silently depended on where the source tree was checked out:
canned blocks generated in one directory would not replay in another
(funding tx output order and nlocktime fuzz diverge, so txids change).
This is why check-doc-examples passed locally but failed in CI.
Hash only the basename: binaries still get distinct seeds, but the
stream no longer depends on the checkout path.
Only in developer mode, ofc.
Notes:
1. We have to move the initialization before the lightningd main trace_start,
since that uses pseudorand().
2. To make the results stable, we need to use per-caller values to randbytes().
Otherwise external timing changes the call order.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
