BUILD: makefile: use $(cmd_MAKE) in quiet mode

It's better to see "make" entering a subdir than seeing nothing, so
let's use a command name for make. Since make 3.81, "+" needs to be
prepended in front of the command to pass the job server to the subdir.
diff --git a/Makefile b/Makefile
index 8baed62..24517e5 100644
--- a/Makefile
+++ b/Makefile
@@ -1008,13 +1008,13 @@
 	$(cmd_LD) $(LDFLAGS) -o $@ $^ $(LDOPTS)
 
 dev/poll/poll:
-	$(Q)$(MAKE) -C dev/poll poll CC='$(CC)' OPTIMIZE='$(COPTS)' V='$(V)'
+	$(cmd_MAKE) -C dev/poll poll CC='$(CC)' OPTIMIZE='$(COPTS)' V='$(V)'
 
 dev/qpack/decode: dev/qpack/decode.o
 	$(cmd_LD) $(LDFLAGS) -o $@ $^ $(LDOPTS)
 
 dev/tcploop/tcploop:
-	$(Q)$(MAKE) -C dev/tcploop tcploop CC='$(CC)' OPTIMIZE='$(COPTS)' V='$(V)'
+	$(cmd_MAKE) -C dev/tcploop tcploop CC='$(CC)' OPTIMIZE='$(COPTS)' V='$(V)'
 
 dev/udp/udp-perturb: dev/udp/udp-perturb.o
 	$(cmd_LD) $(LDFLAGS) -o $@ $^ $(LDOPTS)
diff --git a/include/make/verbose.mk b/include/make/verbose.mk
index 6539747..c37d513 100644
--- a/include/make/verbose.mk
+++ b/include/make/verbose.mk
@@ -12,16 +12,19 @@
 cmd_CC = $(CC)
 cmd_LD = $(LD)
 cmd_AR = $(AR)
+cmd_MAKE = +$(MAKE)
 else
 ifeq (3.81,$(firstword $(sort $(MAKE_VERSION) 3.81)))
 # 3.81 or above
 cmd_CC = $(info $   CC      $@) $(Q)$(CC)
 cmd_LD = $(info $   LD      $@) $(Q)$(LD)
 cmd_AR = $(info $   AR      $@) $(Q)$(AR)
+cmd_MAKE = $(info $   MAKE    $@) $(Q)+$(MAKE)
 else
 # 3.80 or older
 cmd_CC = $(Q)echo "  CC      $@";$(CC)
 cmd_LD = $(Q)echo "  LD      $@";$(LD)
 cmd_AR = $(Q)echo "  AR      $@";$(AR)
+cmd_MAKE = $(Q)echo "  MAKE    $@";$(MAKE)
 endif
 endif