patch 8.1.1380: MS-Windows building VIMDLL with MSVC: SUBSYSTEM is not set

Problem:    MS-Windows building VIMDLL with MSVC: SUBSYSTEM is not set.
Solution:   Invert condition. (closes #4422)
diff --git a/src/Make_mvc.mak b/src/Make_mvc.mak
index 89f4e13..4981539 100644
--- a/src/Make_mvc.mak
+++ b/src/Make_mvc.mak
@@ -847,7 +847,7 @@
 !if "$(SUBSYSTEM_VER)" != ""
 SUBSYSTEM = $(SUBSYSTEM),$(SUBSYSTEM_VER)
 SUBSYSTEM_TOOLS = $(SUBSYSTEM_TOOLS),$(SUBSYSTEM_VER)
-! if "$(VIMDLL)" != "yes"
+! if "$(VIMDLL)" == "yes"
 SUBSYSTEM_CON = $(SUBSYSTEM_CON),$(SUBSYSTEM_VER)
 ! endif
 # Pass SUBSYSTEM_VER to GvimExt and other tools