Binary interface header has changed
Since 47070144 we use ULEB128 encoding (variable length) to store every Int/Word in binary interface files. As a side-effect the interface header has changed:
- magic word: 0x1face or 0x1face64 is now ULEB128 encoded (e.g. 0xe49ceb0f)
- we kept a dummy field (see Note [dummy iface field]) for backward compat reason but we broke it because it's now always a single null byte instead of a 32-/64-bit null word
I don't think it was an intended change.