Add abstract target names for index generation

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/Makefile b/Makefile
index 663df86..f8d26d2 100644
--- a/Makefile
+++ b/Makefile
@@ -142,7 +142,10 @@
 	$(CTAGS) $@ $(C_SOURCE_FILES)
 TAGS: $(C_SOURCE_FILES)
 	etags -o $@ $(C_SOURCE_FILES)
+global: GPATH GRTAGS GSYMS GTAGS
 GPATH GRTAGS GSYMS GTAGS: $(C_SOURCE_FILES)
 	ls $(C_SOURCE_FILES) | gtags -f - --gtagsconf .globalrc
+cscope: cscope.in.out cscope.po.out cscope.out
 cscope.in.out cscope.po.out cscope.out: $(C_SOURCE_FILES)
 	cscope -bq -u -Iinclude -Ilibrary $(patsubst %,-I%,$(wildcard 3rdparty/*/include)) -Itests/include $(C_SOURCE_FILES)
+.PHONY: cscope global