If SwiftLint is built from this state using the Swift SDK, we'll get a
large self-contained Linux executable that runs without loading SourceKit.
It can do that by disabling any rule that requires SourceKit.
With `SWIFTLINT_DISABLE_SOURCEKIT` set on a normally (dynamically linked)
binary, the behavior is the same. That's different from the previously
reported more serious warnings.
With the binding of configurations to their associated rule types
"unknown configuration" errors can be made more specific mentioning
also the rule's identifier in the printed message.
Danny Mösch
Martin Redington
JP Simard