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/os_win32.h b/src/os_win32.h
index 6ebe037..ea10182 100644
--- a/src/os_win32.h
+++ b/src/os_win32.h
@@ -78,7 +78,7 @@
 
 #define HAVE_PUTENV		/* at least Bcc 5.2 and MSC have it */
 
-#ifdef FEAT_GUI_MSWIN
+#if defined(FEAT_GUI_MSWIN) && !defined(VIMDLL)
 # define NO_CONSOLE		/* don't included console-only code */
 #endif