[gtk-doc] Fix maintainer-clean rule

docs/reference/Makefile.am

diff --git a/docs/reference/Makefile.am b/docs/reference/Makefile.am
index 1da46a6..b08ecec 100644
--- a/docs/reference/Makefile.am
+++ b/docs/reference/Makefile.am
@@ -106,7 +106,9 @@
 #TESTS = $(GTKDOC_CHECK)
 endif
 
-maintainer-clean-local:
+maintainer-clean-local: maintainer-clean-tmpl
+
+maintainer-clean-tmpl:
 	-rm -rf $(srcdir)/tmpl
 
 -include $(top_srcdir)/git.mk