Adds target to build only dependencies

Makefile

@@ -22,11 +22,13 @@ export TEXINPUTS := ./texinputs/:$(TEXINPUTS)
 
 #.SECONDARY: $(FIGS_PDF)
 
-.PHONY: all clean toc bibetex
+.PHONY: all clean dep toc bibetex
 
 all: $(TOP)
 
-$(TOP) : $(NEEDED)
+$(TOP) : dep
+
+dep: $(NEEDED)
 
 %.pdf:%.tex
 	@echo "Latex search path $(TEXINPUTS)"