Merge branch 'cmake_improvement' into cmake/fix_installation

Author: Gaspard--

CMakeLists.txt

@@ -71,10 +71,10 @@ if (NOT IDE_BUILD)
   configure_package_config_file(
     "${PROJECT_SOURCE_DIR}/cmake/claws-config.cmake.in"
     "${PROJECT_BINARY_DIR}/claws-config.cmake"
-    INSTALL_DESTINATION lib/cmake/claws
+    INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/claws
     )
 
   install(FILES
     "${PROJECT_BINARY_DIR}/claws-config.cmake"
-    DESTINATION lib/cmake/claws)
+    DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/claws)
 endif()