force to update the cache variable

modules/FindPkgconfigLibrariesAbsolutePath.cmake

@@ -46,6 +46,7 @@ macro(FIND_PKGCONFIG_LIBRARIES_ABSOLUTE_PATH _prefix)
           message(FATAL_ERROR "Dependency of ${_prefix} '${_library}' NOT FOUND")
       endif()
       unset(_library_path CACHE)
+      set (${_prefix}_LIBRARIES "${${_prefix}_LIBRARIES}" CACHE INTERNAL "" FORCE)
   endforeach()
   set(${_prefix}_STATIC_LIBRARIES_COPY "${${_prefix}_STATIC_LIBRARIES}")
   set(${_prefix}_STATIC_LIBRARIES "")
@@ -54,11 +55,12 @@ macro(FIND_PKGCONFIG_LIBRARIES_ABSOLUTE_PATH _prefix)
       find_library(_library_path NAMES ${_library}
           HINTS ${${_prefix}_STATIC_LIBDIR} ${${_prefix}_STATIC_LIBRARY_DIRS} ${_lib_env})
       if (_library_path)
-          list(APPEND ${_prefix}_STATIC_LIBRARIES ${_library_path})
+          list(APPEND ${_prefix}_STATIC_LIBRARIES ${_library_path})	
       else()
           message(FATAL_ERROR "Dependency of ${_prefix} '${_library}' NOT FOUND")
       endif()
       unset(_library_path CACHE)
+      set (${_prefix}_STATIC_LIBRARIES "${${_prefix}_STATIC_LIBRARIES}" CACHE INTERNAL "" FORCE)
   endforeach()
 endmacro()