makefile(all): fix make check exit code (#7609)

close #7608

Makefile

@@ -301,7 +301,7 @@ check-static: tools/bin/golangci-lint
 check: check-copyright fmt check-static tidy terror_check errdoc \
 	check-merge-conflicts check-ticdc-dashboard check-diff-line-width \
 	swagger-spec check-makefiles check_engine_integration_test
-	@git --no-pager diff --exit-code || echo "Please add changed files!"
+	@git --no-pager diff --exit-code || (echo "Please add changed files!" && false)
 
 integration_test_coverage: tools/bin/gocovmerge tools/bin/goveralls
 	tools/bin/gocovmerge "$(TEST_DIR)"/cov.* | grep -vE ".*.pb.go|$(CDC_PKG)/testing_utils/.*|$(CDC_PKG)/cdc/entry/schema_test_helper.go|$(CDC_PKG)/cdc/sink/simple_mysql_tester.go|.*.__failpoint_binding__.go" > "$(TEST_DIR)/all_cov.out"