message: [vcpkg] Use c++experimental in clang
diff: cmake_minimum_required(VERSION 3.3)
  project(vcpkg CXX)
  -add_compile_options(-std=c++1z)
  -
  file(GLOB_RECURSE VCPKGLIB_SOURCES src/vcpkg/*.cpp)
  add_library(vcpkglib STATIC ${VCPKGLIB_SOURCES})
  target_compile_definitions(vcpkglib PRIVATE -DDISABLE_METRICS=0)
  target_include_directories(vcpkglib PUBLIC include)
  +
  +if(CMAKE_COMPILER_IS_GNUXX)
  target_link_libraries(vcpkglib PRIVATE stdc++fs)
  + target_compile_options(vcpkglib PRIVATE -std=c++1z)
  +elseif(CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang")
  + target_link_libraries(vcpkglib PRIVATE c++experimental)
  + target_compile_options(vcpkglib PRIVATE -std=c++1z)
  +endif()
  add_executable(vcpkg src/vcpkg.cpp)
  target_link_libraries(vcpkg PRIVATE vcpkglib)
  