[build]: add arch name in sonic-slave docker image

for exmaple, for arm64, the sonic-slave docker image name
is sonic-slave-arm64-$(USER)

for amd64, the docker image is kept as it is

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

Makefile.work

@@ -91,7 +91,11 @@ endif
 
 include rules/config
 
+ifeq ($(CONFIGURED_ARCH),amd64)
 SLAVE_BASE_IMAGE = $(SLAVE_DIR)
+else
+SLAVE_BASE_IMAGE = $(SLAVE_DIR)-$(CONFIGURED_ARCH)
+endif
 SLAVE_IMAGE = $(SLAVE_BASE_IMAGE)-$(USER)
 
 # Generate the version control build info