[Build] Move build operation completion callback into progress tracker

Author: xedin

Sources/Build/BuildOperation.swift

@@ -391,7 +391,6 @@ public final class BuildOperation: PackageStructureDelegate, SPMBuildCore.BuildS
             duration: duration,
             subsetDescriptor: subsetDescriptor
         )
-        self.delegate?.buildSystem(self, didFinishWithResult: success)
         guard success else { throw Diagnostics.fatalError }
 
         // Create backwards-compatibility symlink to old build path.

Sources/Build/BuildOperationBuildSystemDelegateHandler.swift

@@ -983,6 +983,8 @@ final class LLBuildProgressTracker: LLBuildBuildSystemDelegate, SwiftCompilerOut
 
         queue.sync {
             self.progressAnimation.complete(success: success)
+            self.delegate?.buildSystem(self.buildSystem, didFinishWithResult: success)
+
             if success {
                 let message = cancelled ? "Build \(subsetString)cancelled!" : "Build \(subsetString)complete!"
                 self.progressAnimation.clear()