run-tests: support running tests in parallel on windows

Previously, we used os.spawnvp, which doesn't exist on Windows, and
isn't needed anyway (the command line begins with an absolute path).

We also need a slightly more convoluted way to wait for processes
without specifying an order on Windows, as it lacks os.wait.

tests/run-tests.py

@@ -56,6 +56,7 b' import re'
 import threading
 import killdaemons as killmod
 import cPickle as pickle
+import Queue as queue
 
 processlock = threading.Lock()
 
@@ -1079,7 +1080,13 b' def runchildren(options, tests):'
                 blacklisted.append(test)
             else:
                 job.append(test)
-    fps = {}
+
+    waitq = queue.Queue()
+
+    # windows lacks os.wait, so we must emulate it
+    def waitfor(proc, rfd):
+        fp = os.fdopen(rfd, 'rb')
+        return lambda: waitq.put((proc.pid, proc.wait(), fp))
 
     for j, job in enumerate(jobs):
         if not job:
@@ -1090,16 +1097,18 b' def runchildren(options, tests):'
         childopts += ['--tmpdir', childtmp]
         cmdline = [PYTHON, sys.argv[0]] + opts + childopts + job
         vlog(' '.join(cmdline))
-        fps[os.spawnvp(os.P_NOWAIT, cmdline[0], cmdline)] = os.fdopen(rfd, 'rb')
+        proc = subprocess.Popen(cmdline, executable=cmdline[0])
+        threading.Thread(target=waitfor(proc, rfd)).start()
         os.close(wfd)
     signal.signal(signal.SIGINT, signal.SIG_IGN)
     failures = 0
     passed, skipped, failed = 0, 0, 0
     skips = []
     fails = []
-    while fps:
-        pid, status = os.wait()
-        fp = fps.pop(pid)
+    for job in jobs:
+        if not job:
+            continue
+        pid, status, fp = waitq.get()
         try:
             childresults = pickle.load(fp)
         except pickle.UnpicklingError: