cmake VexCL examples

OPM/opm-simulators CMakeLists.txt :278 

find_package(VexCL)

KratosMultiphysics/Kratos external_libraries/vexcl/examples/simple/CMakeLists.txt :4 

find_package(VexCL)

ddemidov/vexcl examples/simple/CMakeLists.txt :4 

find_package(VexCL)