patch 9.1.0794: tests: tests may fail on Windows environment

Problem:  tests: tests may fail on Windows environment
Solution: use shellcmdflag=/D to skip executing autorun from
          the registry (Milly)

closes: #15900

Signed-off-by: Milly <milly.ca@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_windows_home.vim b/src/testdir/test_windows_home.vim
index 7db5395..ceed25a 100644
--- a/src/testdir/test_windows_home.vim
+++ b/src/testdir/test_windows_home.vim
@@ -105,7 +105,7 @@
       RestoreEnv
       let $HOME = save_home
       let env = ''
-      let job = job_start('cmd /c set', {'out_cb': {ch,x->[env,execute('let env=x')]}})
+      let job = job_start('cmd /D /c set', {'out_cb': {ch,x->[env,execute('let env=x')]}})
       sleep 1
       let env = filter(split(env, "\n"), 'v:val=="HOME"')
       let home = len(env) == 0 ? "" : env[0]