cmake HAVE_ATTR_LIB examples

alibaba/AliSQLBackup storage/innobase/xtrabackup/src/libarchive/CMakeLists.txt :753 

CHECK_LIBRARY_EXISTS(attr "setxattr" "" HAVE_ATTR_LIB)

alibaba/AliSQLBackup storage/innobase/xtrabackup/src/libarchive/CMakeLists.txt :756 

ENDIF(HAVE_ATTR_LIB)