Update amp_is_available() to check for cron & CLI (#5547)

Co-authored-by: Weston Ruter <[email protected]>

Author: roborourke

includes/amp-helper-functions.php

@@ -409,8 +409,8 @@ function amp_add_frontend_actions() {
 function amp_is_available() {
 	global $pagenow, $wp_query;
 
-	// Short-circuit for admin requests or requests to non-frontend pages.
-	if ( is_admin() || in_array( $pagenow, [ 'wp-login.php', 'wp-signup.php', 'wp-activate.php', 'repair.php' ], true ) ) {
+	// Short-circuit for cron, CLI, admin requests or requests to non-frontend pages.
+	if ( wp_doing_cron() || ( defined( 'WP_CLI' ) && WP_CLI ) || is_admin() || in_array( $pagenow, [ 'wp-login.php', 'wp-signup.php', 'wp-activate.php', 'repair.php' ], true ) ) {
 		return false;
 	}