patch 9.1.0760: tests: no error reported, if gen_opt_test.vim fails

Problem:  tests: no error reported, if gen_opt_test.vim fails
Solution: Make Vim exit with return code 1 in case of any error
          (Milly)

closes: #15795

Signed-off-by: Milly <milly.ca@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/Makefile b/src/testdir/Makefile
index b6e8c80..2827f99 100644
--- a/src/testdir/Makefile
+++ b/src/testdir/Makefile
@@ -161,7 +161,7 @@
 	@rm vimcmd
 
 opt_test.vim: ../optiondefs.h gen_opt_test.vim
-	$(VIMPROG) -u NONE -S gen_opt_test.vim --noplugin --not-a-term ../optiondefs.h
+	$(VIMPROG) -e -s -u NONE $(NO_INITS) --nofork --gui-dialog-file guidialog -S gen_opt_test.vim ../optiondefs.h
 
 test_xxd.res:
 	XXD=$(XXDPROG); export XXD; $(RUN_VIMTEST) $(NO_INITS) -S runtest.vim test_xxd.vim