cmake P4EST_HAVE_ZLIB examples

dealii/dealii cmake/modules/FindDEAL_II_P4EST.cmake :130 

file(STRINGS "${P4EST_INCLUDE_DIR}/p4est_config.h" P4EST_ZLIB_STRING
    REGEX "^#define.*P4EST_HAVE_ZLIB")

cburstedde/p4est cmake/config.cmake :97 

check_symbol_exists(adler32_combine zlib.h P4EST_HAVE_ZLIB)