Use -rf with autom4te.cache.
diff --git a/update-autotools b/update-autotools
index 4c6be2f..86dc000 100755
--- a/update-autotools
+++ b/update-autotools
@@ -3,8 +3,8 @@
 # When local system does not have the latest autoconf/automake
 #        -- Kunihiro Ishiguro <kunihiro@zebra.org>
 #
-rm -f config.cache Makefile.in aclocal.m4 config.h.in
-rm -f autom4te.cache configure
+rm -f config.cache Makefile.in aclocal.m4 config.h.in configure
+rm -rf autom4te.cache
 aclocal
 autoheader
 autoconf