oss-fuzz issues 22371 and 22850 incorrectly closed as fixed

[ajakk]

https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=22371
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=22850

An upstream report indicates these issues weren't actually fixed upstream:

keystone-engine/keystone#516

And the commit that ostensibly fixes the oss-fuzz issues don't seem at all relevant - it seems like a small build system patch. I'd test myself, but I wasn't able to figure out how to produce the fuzz target according to this.