misc: add knob to generate compile_commands.json

Used for lanuguage servers like clangd and ccls

Type: improvement
Change-Id: I68d534dfa7b8ba3459fbd919d5ffccaa1fa1171e
Signed-off-by: Damjan Marion <damarion@cisco.com>

.gitignore

@@ -84,6 +84,10 @@ GTAGS
 /sphinx_venv
 !/docs/Makefile
 
+# language servers
+compile_commands.json
+.clangd
+
 # indent backup files
 *.BAK
 

Makefile

@@ -223,6 +223,7 @@ help:
 	@echo " ctags                - (re)generate ctags database"
 	@echo " gtags                - (re)generate gtags database"
 	@echo " cscope               - (re)generate cscope database"
+	@echo " compdb               - (re)generate compile_commands.json"
 	@echo " checkstyle           - check coding style"
 	@echo " checkstyle-commit    - check commit message format"
 	@echo " checkstyle-test      - check test framework coding style"
@@ -654,6 +655,10 @@ gtags: ctags
 cscope: cscope.files
 	@cscope -b -q -v
 
+.PHONY: compdb
+compdb:
+	@ninja -C build-root/build-vpp_debug-native/vpp -t compdb > compile_commands.json
+
 .PHONY: checkstyle
 checkstyle: checkfeaturelist
 	@build-root/scripts/checkstyle.sh