Don't use parallel testing with -j1

diff --git a/run-tests.php b/run-tests.php
index fc40ae8a2f7706ab2657cfe9bb55f9214ce9bb7f..a8dbd81c38ace7a1d7f5a449da7c22d4a6cdf4a0 100755 (executable)
--- a/run-tests.php
+++ b/run-tests.php
@@ -388,6 +388,10 @@ NO_PROC_OPEN_ERROR;
                                                        error("'$workers' is not a valid number of workers, try e.g. -j16 for 16 workers");
                                                }
                                                $workers = intval($workers, 10);
+                                               // Don't use parallel testing infrastructure if there is only one worker.
+                                               if ($workers === 1) {
+                                                       $workers = null;
+                                               }
                                                break;
                                        case 'r':
                                        case 'l':