Cron: Fix undefined variable notice.

Restore `$gmt_time` variable removed in error from [44483].

Props afragen.
Fixes #45870.


Built from https://develop.svn.wordpress.org/trunk@44505


git-svn-id: http://core.svn.wordpress.org/trunk@44336 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-cron.php

@@ -76,6 +76,8 @@ if ( empty( $crons ) ) {
 	die();
 }
 
+$gmt_time = microtime( true );
+
 // The cron lock: a unix timestamp from when the cron was spawned.
 $doing_cron_transient = get_transient( 'doing_cron' );
 

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-alpha-44504';
+$wp_version = '5.1-alpha-44505';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.