Here is an alternative method for doing multiple args. I use it when the arguments are too long for a one liner.
$app = 'C:\Program Files\MSBuild\test.exe'
$arg1 = '/genmsi'
$arg2 = '/f'
$arg3 = '$MySourceDirectory\src\Deployment\Installations.xml'
& $app $arg1 $arg2 $arg3