add files for building containter artifacts

Lifted in large parts from version 9.5 of the SCL postgresql container.

https://github.com/sclorg/postgresql-container

root/usr/libexec/fix-permissions

@@ -0,0 +1,7 @@
+#!/bin/sh
+# Fix permissions on the given directory to allow group read/write of
+# regular files and execute of directories.
+find "$1" -exec chown postgres {} \;
+find "$1" -exec chgrp 0 {} \;
+find "$1" -exec chmod g+rw {} \;
+find "$1" -type d -exec chmod g+x {} +