Incremental: ensure we add post-compile jobs if no new compile jobs are found

rdar://74447605

Author: nkcsgexi

Sources/SwiftDriverExecution/MultiJobExecutor.swift

@@ -220,11 +220,15 @@ public final class MultiJobExecutor {
       if let newJobs = try incrementalCompilationState?
           .collectJobsDiscoveredToBeNeededAfterFinishing(job: job, result: result) {
         let newJobIndices = Self.addJobs(newJobs, to: &jobs, producing: &producerMap)
-        needInputFor(indices: newJobIndices)
-      }
-      else {
-        needInputFor(indices: postCompileIndices)
+        if !newJobIndices.isEmpty {
+          // We discovered new compile jobs to finish
+          needInputFor(indices: newJobIndices)
+          return
+        }
       }
+      // If we find no other compile jobs to finish, we should perform those
+      // post-compile jobs.
+      needInputFor(indices: postCompileIndices)
     }
     fileprivate func needInputFor<Indices: Collection>(indices: Indices)
     where Indices.Element == Int