Use the CMAKE_LINK_SEARCH_START_STATIC and CMAKE_LINK_SEARCH_END_STATIC
variables to initialize the LINK_SEARCH_START_STATIC and
LINK_SEARCH_END_STATIC target properties respectively.
We use a special dedicated structure to store the LINK_LIBRARIES target
property. Do not try to construct a string from a NULL value. Instead
leave the property structure empty when no value is given.
Reported-by: Ghyslain Leclerc <ghleclerc@gmail.com>