CMake: fix broken daemonization and syslog functionality

CMake: fix broken daemonization and syslog functionality

While CMake is not the official way to build OpenVPN on Linux,
it still make sense to support it. Turns out that

  HAVE_SETSID, HAVE_OPENLOG and HAVE_SYSLOG

were not set by CMake configure, and --daemon and syslog
functionality was broken.

While on it, fix compiler error on unused return value of chdir().

Change-Id: I171d55da2be868d961caa1d4491e6f1ed10ebe8a
Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Arne Schwabe <arne-openvpn@rfc2549.org>
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Message-Id: <20230920121519.177949-1-frank@lichtenheld.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg27045.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>