How to rebuild civicrm admin menu?
Found out that the query for creating Support menu [parent item] didn't get executed. Had to run the sql query manually. This fixed the menu issue.

vim civicrm/sql/civicrm_navigation.mysql +605

INSERT INTO civicrm_navigation
    ( domain_id, url, label, name, permission, permission_operator, parent_id, is_active, has_separator, weight )
VALUES
    ( @domainID, NULL, 'Support', 'Support', NULL, '',  NULL, '1', NULL, 110);