cmake HAS_17_EXPERIMENTAL_FS examples

Wargus/wargus CMakeLists.txt :210 

check_cxx_source_compiles("${EXPERIMENTAL_FS_SRC}" HAS_17_EXPERIMENTAL_FS)

Wargus/stratagus CMakeLists.txt :629 

check_cxx_source_compiles("${EXPERIMENTAL_FS_SRC}" HAS_17_EXPERIMENTAL_FS)