gistfile1.php

 'meta_query' => array(
            array(
                'key' => 'product_current_stock',
                'value' => "(SELECT wp_postmeta.meta_value  as min_stock FROM wp_postmeta WHERE wp_postmeta.post_id = wp_posts.ID AND wp_postmeta.meta_key = 'product_minimum_stock')",
                'compare' => '>='
            )
        ),

function _site_get_meta_sql($sql, $queries, $type, $primary_table, $primary_id_column, $context) {
    if(!empty($context->query_vars['unescape']) && !empty($sql['where'])) {
        $sql['where'] = str_replace("\'" . $context->query_vars['unescape'] . "\'", "'" . $context->query_vars['unescape'] . "'", $sql['where']);
    }

    return $sql;
}
add_filter('get_meta_sql', '_site_get_meta_sql', 10, 6);

get_posts(array(
    'unescape'  => 'product_minimum_stock',
    'meta_query' => array(
        array(
            'key' => 'product_current_stock',
            'value' => "(SELECT wp_postmeta.meta_value  as min_stock FROM wp_postmeta WHERE wp_postmeta.post_id = wp_posts.ID AND wp_postmeta.meta_key = 'product_minimum_stock')",
            'compare' => '>='
        )
    ),
));