message: Fix vcpkg build with clang on Linux
diff: @@ -42,7 +42,18 @@ add_executable(vcpkg src/vcpkg.cpp ${VCPKGLIB_SOURCES})
  target_compile_definitions(vcpkg PRIVATE -DDISABLE_METRICS=${DISABLE_METRICS_VALUE})
  target_include_directories(vcpkg PRIVATE include)
  -if(GCC)
  +if(CLANG)
  + include(CheckCXXSourceCompiles)
  + check_cxx_source_compiles("#include <iostream>
  + int main() { return __GLIBCXX__; }" USES_LIBSTDCXX)
  + check_cxx_source_compiles("#include <iostream>
  + int main() { return _LIBCPP_VERSION; }" USES_LIBCXX)
  + if ( NOT USES_LIBSTDCXX AND NOT USES_LIBCXX )
  + message(FATAL_ERROR "Can't find which C++ runtime is in use")
  + endif()
  +endif()
  +
  +if(GCC OR (CLANG AND USES_LIBSTDCXX))
  target_link_libraries(vcpkg PRIVATE stdc++fs)
  elseif(CLANG)
  target_link_libraries(vcpkg PRIVATE c++experimental)
  