Docs: Make code_examples/extensions parallel safe

Author: KrystalDelusion

docs/source/code_examples/extensions/Makefile

@@ -4,8 +4,8 @@ YOSYS ?= ../../../../$(PROGRAM_PREFIX)yosys
 
 .PHONY: all dots examples
 all: dots examples
-dots: test1.dot
-examples: test0.log test1.log test2.log
+dots: test1.dot my_cmd.so
+examples: test0.log test1.log test2.log my_cmd.so
 
 CXXFLAGS=$(shell $(YOSYS)-config --cxxflags)
 DATDIR=$(shell $(YOSYS)-config --datdir)