Trust created for exclusive benefit of employees as part of pension, disability, death or profit-sharing plan

A trust consisting in whole or in part of real property, or personal property, or both heretofore or hereafter created by an employer as part of a pension plan, disability or death benefit plan, profit-sharing plan or other plan for the exclusive benefit of some or all of his employees, to which contributions are made by such employer or employees, or both, for the purpose of distributing to such employees the earnings or the principal, or both earnings and principal, of such trust, shall not be deemed to be invalid as violating any existing law, statutory or otherwise, against perpetuities or suspension of the power of alienation or against the accumulation of income; but such a trust may continue for such time as may be necessary to accomplish the purposes for which it may be created, and such trust may by its terms be made irrevocable, and the interest of any beneficiary thereof may be made nontransferable.