patch 8.1.1230: a lot of code is shared between vim.exe and gvim.exe

Problem:    A lot of code is shared between vim.exe and gvim.exe.
Solution:   Optionally put the shared code in vim.dll. (Ken Takata,
            closes #4287)
diff --git a/src/channel.c b/src/channel.c
index ca83102..aac8656 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -5319,7 +5319,7 @@
     return job_need_end_check(job) || job_channel_still_useful(job);
 }
 
-#if defined(GUI_MAY_FORK) || defined(PROTO)
+#if defined(GUI_MAY_FORK) || defined(GUI_MAY_SPAWN) || defined(PROTO)
 /*
  * Return TRUE when there is any running job that we care about.
  */