cmake HAVE_CXX_EXPERIMENTAL_FILESYSTEM examples

aljen/spaghetti cmake/DetectCxxFilesystem.cmake :41 

try_compile(HAVE_CXX_EXPERIMENTAL_FILESYSTEM
    ${CMAKE_CURRENT_BINARY_DIR}/CMakeTemp/HaveCxxExperimentalFilesystem
    ${CMAKE_CURRENT_BINARY_DIR}/CMakeTemp/test_cxx_experimental_filesystem.cc
    CXX_STANDARD 17
    CXX_STANDARD_REQUIRED ON
    LINK_LIBRARIES ${TEMP_FILESYSTEM_LIBS}
    OUTPUT_VARIABLE OUTPUT
  )

aljen/spaghetti libspaghetti/CMakeLists.txt :16 

elseif (HAVE_CXX_EXPERIMENTAL_FILESYSTEM)