[sonic-slave-buster]: build sonic-slave-buster docker

- add sonic-slave-buster docker
- remove debhelper from buster backports
  debhelper in buster is enough to build smartmontools 6.6

Signed-off-by: Guohan Lu <lguohan@gmail.com>

Author: lguohan

Makefile

@@ -15,6 +15,9 @@ ifeq ($(NOJESSIE), 0)
 	make -f Makefile.work jessie
 endif
 
+buster:
+	BLDENV=buster make -f Makefile.work
+
 clean reset init configure showtag sonic-slave-build sonic-slave-bash :
 	@echo "+++ Making $@ +++"
 ifeq ($(NOJESSIE), 0)

Makefile.work

@@ -76,11 +76,14 @@ ifeq ($(PLATFORM_ARCH),)
 	override PLATFORM_ARCH = $(CONFIGURED_ARCH)
 endif
 
-ifeq ($(BLDENV), stretch)
+ifeq ($(BLDENV), buster)
+SLAVE_DIR = sonic-slave-buster
+else ifeq ($(BLDENV), stretch)
 SLAVE_DIR = sonic-slave-stretch
 else
 SLAVE_DIR = sonic-slave-jessie
 endif
+
 SLAVE_BASE_TAG = $(shell CONFIGURED_ARCH=$(CONFIGURED_ARCH) j2 $(SLAVE_DIR)/Dockerfile.j2 > $(SLAVE_DIR)/Dockerfile && sha1sum $(SLAVE_DIR)/Dockerfile | awk '{print substr($$1,0,11);}')
 SLAVE_TAG = $(shell cat $(SLAVE_DIR)/Dockerfile.user $(SLAVE_DIR)/Dockerfile | sha1sum | awk '{print substr($$1,0,11);}')
 SLAVE_BASE_IMAGE = $(SLAVE_DIR)