add empty m4 dir as workaround for autoreconf issue

Signed-off-by: Andy Green <andy.green@linaro.org>
diff --git a/m4/ignore-me b/m4/ignore-me
new file mode 100644
index 0000000..139597f
--- /dev/null
+++ b/m4/ignore-me
@@ -0,0 +1,2 @@
+
+