patch 8.1.0724: build for MinGW fails

Problem:    Build for MinGW fails.
Solution:   Avoid specifying dependencies in included makefile.
diff --git a/src/testdir/Make_ming.mak b/src/testdir/Make_ming.mak
index 2fa3e78..a2e586f 100644
--- a/src/testdir/Make_ming.mak
+++ b/src/testdir/Make_ming.mak
@@ -127,5 +127,7 @@
 	$(VIMPROG) -u gui_preinit.vim -U gui_init.vim $(NO_PLUGINS) -S runtest.vim $<
 	@$(DEL) vimcmd
 
+test_options.res test_alot.res: opt_test.vim
+
 opt_test.vim: ../option.c gen_opt_test.vim
 	$(VIMPROG) -u NONE -S gen_opt_test.vim --noplugin --not-a-term ../option.c