docs: Makefile tidying

examples and dots are now orthogonal.

docs/source/code_examples/fifo/Makefile

@@ -10,8 +10,10 @@ MAPDOT_NAMES += rdata_map_ffs rdata_map_luts rdata_map_cells
 DOTS := $(addsuffix .dot,$(DOT_NAMES))
 MAPDOTS := $(addsuffix .dot,$(MAPDOT_NAMES))
 
-all: dots fifo.out fifo.stat
+.PHONY: all dots examples
+all: dots examples
 dots: $(DOTS) $(MAPDOTS)
+examples: fifo.out fifo.stat
 
 $(DOTS) fifo.out: fifo.v fifo.ys
 	$(YOSYS) fifo.ys -l fifo.out -Q -T