How do I point to a particular installation of simplesamlphp with the simplesamlphp_auth module?
You can just create a symlink to your temporary SAML folder

ln -s /foo/bar/simplesamlphp ./simplesaml


In settings.php add next line:

$settings['simplesamlphp_dir'] = '/foo/bar/simplesamlphp';


In config.php file in your /simplesamlphp/config library add following settings:

// Load necessary environmental data
$ps = json_decode($_SERVER['PRESSFLOW_SETTINGS'], TRUE);
$host = $_SERVER['HTTP_HOST'];
$db = $ps['databases']['default']['default'];

// Define basic variables
$config = array (
   'baseurlpath' =&gt; 'https://'. $host .':443/simplesaml/', // SAML should always connect via 443
   'certdir' =&gt; 'cert/',
   'loggingdir' =&gt; '/files/private/log/',
   'datadir' =&gt; 'data/',
   'tempdir' =&gt; '/tmp/simplesaml',
   'store.type' =&gt; 'sql',
   'store.sql.dsn' =&gt; 'mysql:host='. $db['host'] .';port='. $db['port'] .';dbname='. $db['database'],
   'store.sql.username' =&gt; $db['username'],
   'store.sql.password' =&gt; $db['password'],
);


Now if you open your-site.com/simplesaml url in the browser, /foo/bar/simplesamlphp library will be used instead of vendor folder.