cmake HAVE_DIRFD examples

libarchive/libarchive CMakeLists.txt :1592

CHECK_C_SOURCE_COMPILES(
  "#include <dirent.h>\nint main() {DIR *d = opendir(\".\"); return dirfd(d);}"
  HAVE_DIRFD)

JulNadeauCA/libagar CMakeChecks.cmake :1016

check_c_source_compiles("
#include <dirent.h>

int
main(int argc, char *argv[])
{
	DIR *dirp = opendir(\"foo\");
	int fd = -1;
	if (dirp != NULL) {
		fd = dirfd(dirp);
		closedir(dirp);
	}
	return (fd == -1);
}
" HAVE_DIRFD)