patch 8.2.2535: MS-Windows: cannot run all vim9 tests

Problem:    MS-Windows: cannot run all vim9 tests.
Solution:   Make test_vim9 target work.
diff --git a/src/Make_mvc.mak b/src/Make_mvc.mak
index dc2f645..257f7e0 100644
--- a/src/Make_mvc.mak
+++ b/src/Make_mvc.mak
@@ -1489,6 +1489,16 @@
 	$(MAKE) /NOLOGO -f Make_dos.mak VIMPROG=..\$(VIMTESTTARGET) report
 	cd ..
 
+# Run Vim9 tests.
+# These do not depend on the executable, compile it when needed.
+test_vim9:
+	cd testdir
+	-del test_vim9_*.res
+	$(MAKE) /NOLOGO -f Make_dos.mak VIMPROG=..\$(VIMTESTTARGET) nolog
+	$(MAKE) /NOLOGO -f Make_dos.mak VIMPROG=..\$(VIMTESTTARGET) $(TEST_VIM9_RES)
+	$(MAKE) /NOLOGO -f Make_dos.mak VIMPROG=..\$(VIMTESTTARGET) report
+	cd ..
+
 ###########################################################################
 
 # Create a default rule for transforming .c files to .obj files in $(OUTDIR)