Add missing target from makefile

The target was missing in the mk file, causing "commands commence before
first target" error.

Test: TH
Change-Id: I0ec4f636daf1171e81bf9c7c764b15e07a25fc80

core/tasks/vendor_snapshot.mk

@@ -95,6 +95,7 @@ vendor-fake-snapshot:
 
 .PHONY: vendor-hwasan-snapshot
 vendor-hwasan-snapshot: PRIVATE_MAKEFILE := $(current_makefile)
+vendor-hwasan-snapshot:
 	$(call echo-error,$(PRIVATE_MAKEFILE),\
 		"CANNOT generate Vendor HWASAN snapshot. BOARD_VNDK_VERSION must be set to 'current'.")
 	exit 1