andymatuschak/Sparkle — comment on commit ec4ebbdcfb5cd5f61aac85040cbd9eb8bf22b169
File: Configurations/ConfigFramework.xcconfig line 8
By triplef:

It looks like the Xcode project still references libcrypto in the Frameworks folder, and at least Xcode 4.2 still links against libcrypto for me despite this change. Removing libcrypto from the project lets it run on 10.5 again.