Could NOT find PNG, but it IS installed.

[LunaMoo]

Don't know that much about cmake, but I think you can ignore the missing things stuff, I belive it only states it can't find those on your system and continues to uses the ones provided, it doesn't have any errors there.

If you look up - to actual CMake error - you'll see the problem is actually with Snappy, not PNG, so #9443 is most likely your issue. As you can see Orphis already said he'll check it and he's on the other hand definitely a CMake expert, so maybe just subscribe to that issue and wait.