Cross Reference: /external/libcxx/test/std/thread/thread.mutex/thread.once

`Name`	`Date`	`Size`
Up to higher level directory
`nothing_to_do.pass.cpp`	21-Aug-2018	`372`
`thread.once.callonce/`	21-Aug-2018
`thread.once.onceflag/`	21-Aug-2018