[build]: Fixes the DPKG cache break because of SAI package content ch…

…anges without changing its version (sonic-net#5651)

- The issue is that the SAI package content is changed without changing its version. The DPKG caches the wrong version of SAI package. 
- The fix is to include the SAI package content header for SHA calcaulation. This will detect if there is any change in the SAI package.

platform/broadcom/sai.dep

@@ -3,12 +3,16 @@
 SPATH       := $($(BRCM_SAI)_SRC_PATH)
 DEP_FILES   := $(SONIC_COMMON_FILES_LIST) platform/broadcom/sai.mk platform/broadcom/sai.dep   
 DEP_FILES   += $(SONIC_COMMON_BASE_FILES_LIST)
+# Get the Latest HTTP Header and calculate the SHA value as it is a softlink that always points to LATEST_INT_OCP_SAI_X.X.X
+SAI_FLAGS   := $(shell wget --spider --server-response $($(BRCM_SAI)_URL) $($(BRCM_SAI_DEV)_URL)  2>&1 \
+			   | grep -Ev -- '--|Date:'|sha256sum|awk '{print $$1}' )
 
 $(BRCM_SAI)_CACHE_MODE  := GIT_CONTENT_SHA 
-$(BRCM_SAI)_DEP_FLAGS   := $(SONIC_COMMON_FLAGS_LIST)
+$(BRCM_SAI)_DEP_FLAGS   := $(SONIC_COMMON_FLAGS_LIST) $(SAI_FLAGS)
 $(BRCM_SAI)_DEP_FILES   := $(DEP_FILES)
 
+
 $(BRCM_SAI_DEV)_CACHE_MODE  := GIT_CONTENT_SHA 
-$(BRCM_SAI_DEV)_DEP_FLAGS   := $(SONIC_COMMON_FLAGS_LIST)
+$(BRCM_SAI_DEV)_DEP_FLAGS   := $(SONIC_COMMON_FLAGS_LIST) $(SAI_FLAGS)
 $(BRCM_SAI_DEV)_DEP_FILES   := $(DEP_FILES)