patch 8.2.4294: MS-Windows: #ifdefs for Cygwin are too complicated

Problem:    MS-Windows: #ifdefs for Cygwin are too complicated.
Solution:   Simplify the conditions. (Ken Takata, closes #9693)
diff --git a/src/os_unix.c b/src/os_unix.c
index 9848698..cbd8ba8 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -44,15 +44,13 @@
 #endif
 
 #ifdef __CYGWIN__
-# ifndef MSWIN
-#  include <cygwin/version.h>
-#  include <sys/cygwin.h>	// for cygwin_conv_to_posix_path() and/or
+# include <cygwin/version.h>
+# include <sys/cygwin.h>	// for cygwin_conv_to_posix_path() and/or
 				// for cygwin_conv_path()
-#  ifdef FEAT_CYGWIN_WIN32_CLIPBOARD
-#   define WIN32_LEAN_AND_MEAN
-#   include <windows.h>
-#   include "winclip.pro"
-#  endif
+# ifdef FEAT_CYGWIN_WIN32_CLIPBOARD
+#  define WIN32_LEAN_AND_MEAN
+#  include <windows.h>
+#  include "winclip.pro"
 # endif
 #endif