patch 8.2.2035: MS-Windows: some tests may fail

Problem:    MS-Windows: some tests may fail.
Solution:   Avoid test failures. (Yegappan Lakshmanan, closes #7346)
diff --git a/src/testdir/test_channel.vim b/src/testdir/test_channel.vim
index 90d828b..e9cc258 100644
--- a/src/testdir/test_channel.vim
+++ b/src/testdir/test_channel.vim
@@ -2304,8 +2304,14 @@
 func Test_cb_with_input()
   let g:wait_exit_cb = 1
 
-  call job_start('echo "Vim''s test"',
-        \ {'out_cb': 'ExitCb_cb_with_input'})
+  if has('win32')
+    let cmd = 'cmd /c echo "Vim''s test"'
+  else
+    let cmd = 'echo "Vim''s test"'
+  endif
+
+  let job = job_start(cmd, {'out_cb': 'ExitCb_cb_with_input'})
+  call WaitFor({-> job_status(job) == "dead"})
   call WaitForAssert({-> assert_equal(0, g:wait_exit_cb)})
 
   unlet g:wait_exit_cb