[Ninja] Optimize evaluation lookup callbacks.
[Ninja] Optimize evaluation lookup callbacks.

 - Provide a user context and lift out to a static method to avoid the lambda
   allocation.

apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild