cmake HAVE__EXIT examples

nghttp2/nghttp2 CMakeLists.txt :379 

check_function_exists(_Exit     HAVE__EXIT)

fluent/fluent-bit lib/nghttp2-1.65.0/CMakeLists.txt :363 

check_function_exists(_Exit     HAVE__EXIT)

Cisco-Talos/clamav CMakeLists.txt :799 

check_symbol_exists(_Exit           "stdlib.h"      HAVE__EXIT)