docker: Don't allocate tty unless DEBUG=1

The existence of tty in the container seems to urge gcc into colorizing
the errors, but the escape chars will clutter the report once turned
into email replies on patchew. Move -t to debug mode.

Reported-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Message-Id: <20171013011954.9975-1-famz@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Fam Zheng <famz@redhat.com>

tests/docker/Makefile.include

@@ -134,10 +134,10 @@ docker-run: docker-qemu-src
 			"  COPYING $(EXECUTABLE) to $(IMAGE)"))
 	$(call quiet-command,						\
 		$(SRC_PATH)/tests/docker/docker.py run 			\
-			$(if $(NOUSER),,-u $(shell id -u)) -t 		\
+			$(if $(NOUSER),,-u $(shell id -u)) 		\
 			--security-opt seccomp=unconfined		\
 			$(if $V,,--rm) 					\
-			$(if $(DEBUG),-i,)				\
+			$(if $(DEBUG),-ti,)				\
 			$(if $(NETWORK),$(if $(subst $(NETWORK),,1),--net=$(NETWORK)),--net=none) \
 			-e TARGET_LIST=$(TARGET_LIST) 			\
 			-e EXTRA_CONFIGURE_OPTS="$(EXTRA_CONFIGURE_OPTS)" \