Refine pylibfdt_clean target

Move it to the subdir Makefile, generalize some of the patterns, remove
the 'build' directory made by setup.py and __pycache__ directory made by
Python3.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Makefile

@@ -271,10 +271,6 @@ include $(PYLIBFDT_srcdir)/Makefile.pylibfdt
 .PHONY: pylibfdt
 pylibfdt: $(PYLIBFDT_objdir)/_libfdt.so
 
-pylibfdt_clean:
-	@$(VECHO) CLEAN "(pylibfdt)"
-	rm -f $(addprefix $(PYLIBFDT_objdir)/,$(PYLIBFDT_cleanfiles))
-
 #
 # Release signing and uploading
 # This is for maintainer convenience, don't try this at home.

pylibfdt/Makefile.pylibfdt

@@ -3,6 +3,10 @@
 
 PYLIBFDT_srcs = $(PYLIBFDT_srcdir)/libfdt.i
 PYMODULE = $(PYLIBFDT_objdir)/_libfdt.so
+PYLIBFDT_CLEANFILES_L = libfdt_wrap.c libfdt.py *.pyc *.so
+PYLIBFDT_CLEANFILES = $(PYLIBFDT_CLEANFILES_L:%=$(PYLIBFDT_objdir)/%)
+PYLIBFDT_CLEANDIRS_L = build __pycache__
+PYLIBFDT_CLEANDIRS = $(PYLIBFDT_CLEANDIRS_L:%=$(PYLIBFDT_objdir)/%)
 
 SETUP = $(PYLIBFDT_srcdir)/setup.py
 SETUPFLAGS =
@@ -19,4 +23,7 @@ install_pylibfdt: $(PYMODULE)
 	@$(VECHO) INSTALL-PYLIB
 	$(PYTHON) $(SETUP) $(SETUPFLAGS) install $(if $(SETUP_PREFIX),--prefix=$(SETUP_PREFIX))
 
-PYLIBFDT_cleanfiles = libfdt_wrap.c libfdt.py libfdt.pyc _libfdt.so
+pylibfdt_clean:
+	@$(VECHO) CLEAN "(pylibfdt)"
+	rm -f $(PYLIBFDT_CLEANFILES)
+	rm -rf $(PYLIBFDT_CLEANDIRS)