Rm warning, improve a diagnostic

Author: David Ungar

Sources/SwiftDriver/IncrementalCompilation/IncrementalCompilationState.swift

@@ -443,7 +443,7 @@ extension IncrementalCompilationState {
             fatalError("Dependent \(dependent) does not have dependencies file!")
           }
           reporter?.report(
-            "Queuing because of external dependency on newer \(extDep.file?.basename ?? "extDep?")",
+            "Queuing because of \(forIncrementalExternalDependencies ? "incremental " : "")external dependency on newer \(extDep.file?.basename ?? "extDep?")",
             path: dependencySource.typedFile)
           externalDependencySources.insert(dependencySource)
         }

Sources/SwiftDriver/IncrementalCompilation/ModuleDependencyGraph.swift

@@ -176,7 +176,6 @@ extension ModuleDependencyGraph {
   ) -> Integrator.Results? {
     guard let file = incrementalExternalDependency.file
      else {
-      #warning("right?")
       diagnosticEngine.emit(warning: "Cannot get file for externalDependency \(incrementalExternalDependency.fileName)")
       return nil
     }