Dynamic Control in customiser

I need to build a select on my theme customise screen from this foreach:

foreach($wp_registered_sidebars as $sidebar_id => $sidebar)
{
    if($sidebar_id == $val)

    $sidebar_id.$sidebar['name']
}

Here is the code for the setting and control for custom sidebar selection.

The dynamic list would need to go in the 'choices' => array();

Is this even possible?

    // Add Layout setting
$wp_customize->add_setting(
    // ID
    'sidebar_left_selection',
    // Arguments array
    array(
        'default' => 'none',
        'type' => 'option',
    )
);

// Add Layout control
$wp_customize->add_control(
    // ID
    'sidebar_left_selection',
    // Arguments array
    array(
        'type' => 'select',
        'label' => __( 'Sidebar Left Selection', 'webcodexcustomizer' ),
        'section' => 'layout_section',
        'choices' => array(
            'none' => __( 'None', 'webcodexcustomizer' ),
            'sidebar_test' => __( 'Test Sidebar', 'webcodexcustomizer' ),
        ),
        'priority' => 36
    )
);