build: fix build for new autoconf

The path for the m4 directory wasn't correct, causing autoreconf to
fail for automake 1.13, which doesn't create AC_CONFIG_MACRO_DIR
automatically.  See https://bugzilla.redhat.com/show_bug.cgi?id=901333
for details.

Change-Id: I33ddf7bcf950411ddc89e88b3ebc3d99df5ff617
Signed-off-by: Greg Padgett <gpadgett@redhat.com>