[sonic-frr] Improve the command to generate dependent files for frr submodule in frr.dep

Issue Description
  In frr.dep, it lists the dependent files for the submodules through
  'git ls-files' and filter the symbolic links through 'grep' with
  explicitly patterns. The patterns might need to be adjusted upon
  each frr version upgrade.

Enhancement
  The dependent files can be found by using 'find' to list all of the
  'file' under the 'frr' submodule directory and pass the file to
  'git ls-files' to know whether the file is included in the git
  control.

Signed-off-by: Charlie Chen <[email protected]>

Author: CharlieChenEC

rules/frr.dep

@@ -1,24 +1,25 @@
 
 SPATH       := $($(FRR)_SRC_PATH)
-DEP_FILES   := $(SONIC_COMMON_FILES_LIST) rules/frr.mk rules/frr.dep   
+DEP_FILES   := $(SONIC_COMMON_FILES_LIST) rules/frr.mk rules/frr.dep
 DEP_FILES   += $(SONIC_COMMON_BASE_FILES_LIST)
 DEP_FILES   += $(addprefix $(SPATH)/,$(shell cd $(SPATH) && git ls-files |grep -Ev '^frr$$$$'))
 
 # Account for source files under the frr submodule directory as well.
-# Remove all the symbolic link files
+# The directories under frr submodule directory need to be filtered out because
+# the checksum cannot be generated against directories
 FRR_SPATH   := $(SPATH)/frr
-SMDEP_FILES := $(addprefix $(FRR_SPATH)/,$(shell cd $(FRR_SPATH) && git ls-files \
-			| grep -Ev -e 'debian/changelog$$$$' \
-			-e '^tests/topotests/bgp_instance_del_test/ce[0-9]$$$$' \
-			-e '^tests/topotests/bgp_instance_del_test/r[0-9]$$$$' \
-			-e '^tests/topotests/bgp_instance_del_test/scripts$$$$' \
-			-e '^tests/topotests/bgp_instance_del_test/customize.py$$$$' \
-			-e '^tests/topotests/bgp_rfapi_basic_sanity_config2/customize.py$$$$' \
-			-e '^tests/topotests/bgp_rfapi_basic_sanity_config2/scripts$$$$' \
-			-e '^tests/topotests/bgp_rfapi_basic_sanity_config2/test_bgp_rfapi_basic_sanity_config2.py$$$$' \
+# Use find to search the type 'file' with git ls-files under FRR_SPATH
+# to enumerate those managed by git
+SMDEP_FILES := $(addprefix $(FRR_SPATH)/,$(shell cd $(FRR_SPATH) &&  \
+			find . -type f -exec git ls-files '''{}''' ';' \
+			))
+# Use find to search the type 'symbolic to file' with git ls-files under FRR_SPATH
+# to enumerate those managed by git
+SMDEP_FILES += $(addprefix $(FRR_SPATH)/,$(shell cd $(FRR_SPATH) && \
+			find . -xtype f -exec test -h '''{}''' ';' -exec git ls-files '''{}''' ';' \
 			))
 
-$(FRR)_CACHE_MODE  := GIT_CONTENT_SHA 
+$(FRR)_CACHE_MODE  := GIT_CONTENT_SHA
 $(FRR)_DEP_FLAGS   := $(SONIC_COMMON_FLAGS_LIST)
 $(FRR)_DEP_FILES   := $(DEP_FILES)
 $(FRR)_SMDEP_FILES := $(SMDEP_FILES)