cmake HAVE_MAP_ANONYMOUS examples

alibaba/AliSQL storage/tokudb/ft-index/cmake_modules/TokuFeatureDetection.cmake :58 

check_symbol_exists(MAP_ANONYMOUS "sys/mman.h" HAVE_MAP_ANONYMOUS)

percona/PerconaFT cmake_modules/TokuFeatureDetection.cmake :59 

check_symbol_exists(MAP_ANONYMOUS "sys/mman.h" HAVE_MAP_ANONYMOUS)

oscarlab/betrfs cmake_modules/TokuFeatureDetection.cmake :63 

check_symbol_exists(MAP_ANONYMOUS "sys/mman.h" HAVE_MAP_ANONYMOUS)