Fix generated dll duplicate reference. (#2935)

Author: timcassell

src/BenchmarkDotNet/Toolchains/CsProj/CsProjGenerator.cs

@@ -161,11 +161,17 @@ public static int Main(string[] args)
 
             if (!buildResult.IsBuildSuccess)
             {
-                throw buildResult.TryToExplainFailureReason(out string reason)
-                    ? new Exception(reason)
-                    : new Exception(buildResult.ErrorMessage);
+                if (!buildResult.TryToExplainFailureReason(out string reason))
+                {
+                    reason = buildResult.ErrorMessage;
+                }
+                logger.WriteLineWarning($"Failed to gather assembly references, reason:{Environment.NewLine}{reason}");
+                return;
             }
 
+            // Delete the dll from the gatherer project to prevent duplicate references.
+            File.Delete(Path.Combine(artifactsPaths.BinariesDirectoryPath, $"{artifactsPaths.ProgramName}.dll"));
+
             xmlDoc = new XmlDocument();
             xmlDoc.Load(artifactsPaths.ProjectFilePath);
             projectElement = xmlDoc.DocumentElement;