Make sure first run results are not overwritten before use

src/Tools/Source/RunTests/ProcessTestExecutor.cs

@@ -94,22 +94,26 @@ private async Task<TestResult> RunTestAsyncInternal(AssemblyInfo assemblyInfo, b
                 // NOTE: xUnit doesn't always create the log directory
                 Directory.CreateDirectory(resultsDir);
 
-                // NOTE: xUnit seems to have an occasional issue creating logs create
-                // an empty log just in case, so our runner will still fail.
-                File.Create(resultsFilePath).Close();
-
                 // Define environment variables for processes started via ProcessRunner.
                 var environmentVariables = new Dictionary<string, string>();
                 Options.ProcDumpInfo?.WriteEnvironmentVariables(environmentVariables);
 
                 if (retry)
                 {
+                    // Copy the results file path, since the new xunit run will overwrite it
+                    var backupResultsFilePath = Path.ChangeExtension(resultsFilePath, ".old");
+                    File.Copy(resultsFilePath, backupResultsFilePath, overwrite: true);
+
                     ConsoleUtil.WriteLine("Starting a retry. It will run once again tests failed.");
                     // If running the process with this varialbe added, we assume that this file contains 
                     // xml logs from the first attempt.
-                    environmentVariables.Add("OutputXmlFilePath", GetResultsFilePath(assemblyInfo));
+                    environmentVariables.Add("OutputXmlFilePath", backupResultsFilePath);
                 }
 
+                // NOTE: xUnit seems to have an occasional issue creating logs create
+                // an empty log just in case, so our runner will still fail.
+                File.Create(resultsFilePath).Close();
+
                 var start = DateTime.UtcNow;
                 var xunitProcessInfo = ProcessRunner.CreateProcess(
                     ProcessRunner.CreateProcessStartInfo(