cmake HAVE_LIBSYSTEMD examples

TigerVNC/tigervnc CMakeLists.txt :373 

add_definitions(-DHAVE_LIBSYSTEMD)

Tinob/Ishiiruka CMakeLists.txt :753 

add_definitions(-DHAVE_LIBSYSTEMD)

fluent/fluent-bit lib/nghttp2-1.65.0/src/CMakeLists.txt :163 

target_compile_definitions(nghttpx_static PUBLIC HAVE_LIBSYSTEMD)