spec/bundler needs the specific command [ci skip]

defs/gmake.mk

@@ -292,6 +292,9 @@ rdoc\:%: PHONY
 test_%.rb test/%: programs PHONY
 	+$(Q)$(exec) $(RUNRUBY) "$(TESTSDIR)/runner.rb" --ruby="$(RUNRUBY)" $(TEST_EXCLUDES) $(TESTOPTS) -- $(patsubst test/%,%,$@)
 
+spec/bundler/%: PHONY
+	+$(Q)$(exec) $(XRUBY) -C $(srcdir) -Ispec/bundler .bundle/bin/rspec --require spec_helper $(RSPECOPTS) $@
+
 spec/%: programs exts PHONY
 	+$(RUNRUBY) -r./$(arch)-fake $(srcdir)/spec/mspec/bin/mspec-run -B $(srcdir)/spec/default.mspec $(SPECOPTS) $(patsubst %,$(srcdir)/%,$@)