1. VXWorks has no fork/exec semantics.

    2. VXWorks has no user database maniuplation.

    3. VXWorks has no file ownership management.

    4. VXWorks has no popen(), but it is only needed in one test.

    5. floating points types are broken (printf does not work and they sometimes
       exhibit strange behavior).

    6. The vxworks target start with its clock set to epoch.