cmake HEADLESS_HAS_EGL examples

STORM-IRIT/Radium-Engine examples/HeadlessExample/CMakeLists.txt :59 

get_target_property(HEADLESS_HAS_EGL Radium::Headless HEADLESS_HAS_EGL)

STORM-IRIT/Radium-Engine src/Headless/CMakeLists.txt :52 

target_compile_definitions(${ra_headless_target} PUBLIC HEADLESS_HAS_EGL)

STORM-IRIT/Radium-Engine src/Headless/CMakeLists.txt :55 

set_target_properties(${ra_headless_target} PROPERTIES HEADLESS_HAS_EGL ${HEADLESS_HAS_EGL})