configure.ac: Add AC_CONFIG_MACRO_DIR

Otherwise macros in m4 directory are not found on autoreconf

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
diff --git a/configure.ac b/configure.ac
index ceb1d18..0e1c3b8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3,6 +3,7 @@
 AC_CONFIG_AUX_DIR([.])
 AM_INIT_AUTOMAKE
 AC_CONFIG_HEADERS([include/config.h])
+AC_CONFIG_MACRO_DIR([m4])
 AC_CONFIG_FILES([ \
     include/mk/config.mk \
     include/mk/features.mk \