Add --tempdir option for test run (GH-10322)

diff --git a/Lib/test/libregrtest/cmdline.py b/Lib/test/libregrtest/cmdline.py
index 538ff05..0927032 100644
--- a/Lib/test/libregrtest/cmdline.py
+++ b/Lib/test/libregrtest/cmdline.py
@@ -271,7 +271,8 @@
     group.add_argument('--junit-xml', dest='xmlpath', metavar='FILENAME',
                        help='writes JUnit-style XML results to the specified '
                             'file')
-
+    group.add_argument('--tempdir', dest='tempdir', metavar='PATH',
+                       help='override the working directory for the test run')
     return parser
 
 
@@ -383,8 +384,7 @@
     if ns.match_filename:
         if ns.match_tests is None:
             ns.match_tests = []
-        filename = os.path.join(support.SAVEDCWD, ns.match_filename)
-        with open(filename) as fp:
+        with open(ns.match_filename) as fp:
             for line in fp:
                 ns.match_tests.append(line.strip())