cmake OpenThreads examples

fzi-forschungszentrum-informatik/gpu-voxels icmaker/CorePackages.cmake :162

FIND_PACKAGE(OpenThreads)

dartsim/dart cmake/DARTFindOpenSceneGraph.cmake :35

find_package(OpenThreads QUIET)

hlrs-vis/covise cmake/Using/UseOPENTHREADS.cmake :2

FIND_PACKAGE(OpenThreads)