ConfigureChecks: VxWorks:  Disable _XOPEN_SOURCE due to "sys/select.h" failing
ConfigureChecks: VxWorks:  Disable _XOPEN_SOURCE due to "sys/select.h" failing

Reported by Martin Oberhuber as V7COR-4651

adrianbroher/python-cmake-buildsystem,thewtex/python-cmake-buildsystem,python-cmake-buildsystem/python-cmake-buildsystem,davidsansome/python-cmake-buildsystem,thewtex/python-cmake-buildsystem