cmake HAVE_WMEMCMP examples

libarchive/libarchive CMakeLists.txt :1573 

CHECK_FUNCTION_EXISTS(wmemcmp HAVE_WMEMCMP)

alibaba/AliSQLBackup storage/innobase/xtrabackup/src/libarchive/CMakeLists.txt :523 

CHECK_SYMBOL_EXISTS(wmemcmp "wchar.h" HAVE_WMEMCMP)