FindMorseCommon: replace FATAL_ERROR by WARNING, libraries may be given without extension at all

modules/find/FindMorseCommon.cmake

@@ -358,7 +358,7 @@ macro(morse_find_pkgconfig_libraries_absolute_path _prefix)
       if (${_prefix}_STATIC)
         message(STATUS "${_prefix}_STATIC ${${_prefix}_STATIC}")
       endif()
-      message(FATAL_ERROR "Dependency of ${_prefix} '${_library}' NOT FOUND with suffixes ${CMAKE_FIND_LIBRARY_SUFFIXES} in ${${_prefix}_LIBDIR} ${${_prefix}_LIBRARY_DIRS}")
+      message(WARNING "Dependency of ${_prefix} '${_library}' NOT FOUND with suffixes ${CMAKE_FIND_LIBRARY_SUFFIXES} in ${${_prefix}_LIBDIR} ${${_prefix}_LIBRARY_DIRS}")
     endif()
 
     unset(_library_path CACHE)