C#: Add directory override.

Author: michaelnebel

csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/DependencyDirectory.cs

@@ -46,5 +46,7 @@ public void Dispose()
                 logger.LogInfo($"Couldn't delete {userReportedDirectoryPurpose} directory {exc.Message}");
             }
         }
+
+        public override string ToString() => DirInfo.FullName.ToString();
     }
 }

csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/NugetPackageRestorer.cs

@@ -49,7 +49,7 @@ public NugetPackageRestorer(
             this.compilationInfoContainer = compilationInfoContainer;
 
             PackageDirectory = new DependencyDirectory("packages", "package", logger);
-            legacyPackageDirectory = new DependencyDirectory("legacypackages", "legacy package", logger);
+            legacyPackageDirectory = new DependencyDirectory(ComputeTempDirectoryPath("legacypackages"), "legacy package", logger);
             missingPackageDirectory = new DependencyDirectory("missingpackages", "missing package", logger);
         }