Check if the -wrap argument is actually supported by the platform's ld

Check if the -wrap argument is actually supported by the platform's ld

This avoids build errors on macOS. Also the test_tls_crypt command works
just fine on FreeBSD with its linkers, so do not make that test Linux only.

Patch v2: allow running with old cmake version (cmake 3 on RHEL7 with EPEL
          is only 3.17)
Patch v3: add OPTIONAL keyword to Incldue required by some cmake versions

Change-Id: Id26676bdc576c7d3d6726afa43fe6c7a397c579b
Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Message-Id: <20230712095529.570306-1-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg26850.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>