message: Use pkg_get_variable() for wayland-protocols dir
  The CMake function uses cross-compilation setup of the project so it
  finds protocols available for the target system.
diff: -cmake_minimum_required(VERSION 2.8 FATAL_ERROR)
  +cmake_minimum_required(VERSION 3.4 FATAL_ERROR)
  cmake_policy(VERSION 2.8)
  set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake")
  @@ -75,7 +75,7 @@ ELSEIF(LINUX)
  endif ()
  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DVK_USE_PLATFORM_WAYLAND_KHR")
  include_directories(${WAYLAND_INCLUDE_DIR})
  - execute_process(COMMAND ${PKG_CONFIG} --variable=pkgdatadir wayland-protocols OUTPUT_VARIABLE protocol_dir OUTPUT_STRIP_TRAILING_WHITESPACE)
  + pkg_get_variable(protocol_dir wayland-protocols pkgdatadir)
  execute_process(COMMAND ${WAYLAND_SCANNER} client-header ${protocol_dir}/stable/xdg-shell/xdg-shell.xml ${CMAKE_BINARY_DIR}/xdg-shell-client-protocol.h
  COMMAND ${WAYLAND_SCANNER} private-code ${protocol_dir}/stable/xdg-shell/xdg-shell.xml ${CMAKE_BINARY_DIR}/xdg-shell-protocol.c)
  include_directories(${CMAKE_BINARY_DIR})
  