Address review comments.

Author: David Ungar

Sources/SwiftDriver/IncrementalCompilation/IncrementalCompilationState.swift

@@ -49,7 +49,7 @@ public final class IncrementalCompilationState {
   /// Can compare input mod times against this.
   private let buildStartTime: Date
 
-  /// In order to decide while postCompile jobs to run, need to compile their outputs against the build time
+  /// In order to decide while postCompile jobs to run, need to compare their outputs against the build time
   private let buildEndTime: Date
 
   private let fileSystem: FileSystem
@@ -310,7 +310,7 @@ extension IncrementalCompilationState {
   public func canSkipPostCompile(job: Job) -> Bool {
     job.outputs.allSatisfy {output in
       let fileModTime = (try? fileSystem.lastModificationTime(for: output.file)) ?? .distantFuture
-      return fileModTime < buildEndTime}
+      return fileModTime <= buildEndTime}
   }
 }