cmake HAVE_LIBBACKTRACE examples

glKarin/com.n0n3m4.diii4a Q3E/src/main/jni/doom3/neo/CMakeLists.txt :432

check_c_source_compiles( "#include <backtrace.h>
	int main() { backtrace_create_state(NULL, 0, NULL, NULL); return 0; }" HAVE_LIBBACKTRACE )