Makefile: add support for setup.py in targets link/clean

The `link` and `clean` targets, very useful under development
environments, have supported directories containing `Makefiles`.

It turns out that for some plugins it may be enough (and more
Pythonic) to just have `setup.py` files, so let's support that.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

Makefile

@@ -103,7 +103,10 @@ clean:
 	rm -rf docs/build
 	find docs/source/api/ -name '*.rst' -delete
 	for MAKEFILE in $(AVOCADO_PLUGINS); do\
-		if test -f $$MAKEFILE/Makefile; then AVOCADO_DIRNAME=$(AVOCADO_DIRNAME) make -C $$MAKEFILE unlink &>/dev/null && echo ">> UNLINK $$MAKEFILE" || echo ">> SKIP $$MAKEFILE"; fi;\
+		if test -f $$MAKEFILE/Makefile -o -f $$MAKEFILE/setup.py; then echo ">> UNLINK $$MAKEFILE";\
+			if test -f $$MAKEFILE/Makefile; then AVOCADO_DIRNAME=$(AVOCADO_DIRNAME) make -C $$MAKEFILE unlink &>/dev/null;\
+			elif test -f $$MAKEFILE/setup.py; then cd $$MAKEFILE; $(PYTHON) setup.py develop --uninstall $(shell $(PYTHON26) || echo --user); cd -; fi;\
+		else echo ">> SKIP $$MAKEFILE"; fi;\
 	done
 	$(PYTHON) setup.py develop --uninstall $(shell $(PYTHON26) || echo --user)
 	rm -rf avocado.egg-info
@@ -152,7 +155,10 @@ develop:
 
 link: develop
 	for MAKEFILE in $(AVOCADO_PLUGINS); do\
-		if test -f $$MAKEFILE/Makefile; then AVOCADO_DIRNAME=$(AVOCADO_DIRNAME) make -C $$MAKEFILE link &>/dev/null && echo ">> LINK $$MAKEFILE" || echo ">> SKIP $$MAKEFILE"; fi;\
+		if test -f $$MAKEFILE/Makefile -o -f $$MAKEFILE/setup.py; then echo ">> LINK $$MAKEFILE";\
+			if test -f $$MAKEFILE/Makefile; then AVOCADO_DIRNAME=$(AVOCADO_DIRNAME) make -C $$MAKEFILE link &>/dev/null;\
+			elif test -f $$MAKEFILE/setup.py; then cd $$MAKEFILE; $(PYTHON) setup.py develop $(shell $(PYTHON26) || echo --user); cd -; fi;\
+		else echo ">> SKIP $$MAKEFILE"; fi;\
 	done
 
 spell: