Malicious or malformed LLB definitions could reference negative or
out-of-range op input indices, or omit required diff lower/upper
inputs, causing the daemon to panic on a slice index or nil pointer
dereference during load and cache-key computation.
Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
(cherry picked from commit 2177ce16335f943e82458958902f9f21f6993d8d)
(cherry picked from commit ed777881d1)
4a31f56030