conf: use Wno-portability

This is required when using newer autoconf-archive and
aaminclude_static.am.

Change-Id: Icc381b65f9ca76d30337c822c55cafd30921acd0
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/configure.ac b/configure.ac
index 620d904..3ff4bf4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3,7 +3,7 @@
 AC_INIT([sys-ipmi], [0.1], [https://www.github.com/google-ipmi-sys/issues])
 AC_LANG([C++])
 AC_CONFIG_HEADERS([config.h])
-AM_INIT_AUTOMAKE([subdir-objects -Wall -Werror foreign dist-xz])
+AM_INIT_AUTOMAKE([subdir-objects -Wall -Werror -Wno-portability foreign dist-xz])
 AM_SILENT_RULES([yes])
 
 # Make sure the default CFLAGS of `-O2 -g` don't override CODE_COVERAGE_CFLAGS