Disable install() directives with non-needed components. (#1268)

  - These install statements do not actually install anything because we
    have specified EXCLUDE_FROM_ALL when adding the xerces subdirectory
    in the CMakeLists file.

    Unfortunately, the install component they create (in this case called
    `development`) is added to the final list of install components.
    This causes a generation of an empty package named `development` when
    we use cpack to generate packages for OpenModelica.

Author: mahge