work around false positive warning with mingw 12

work around false positive warning with mingw 12

When cross compiling for Windows with Ubuntu 23.04 mingw complains about

  route.c:344:26: warning: ‘special.S_un.S_addr’ may be used uninitialized

which is wrong technically. However the workaround isn't really
intrusive and while there are other warnings caused by libtool, the
cmake mingw build completes with -Werror now.

Change-Id: I8a0f59707570722eab41af2db76980ced04e6d54
Signed-off-by: Heiko Hund <heiko@ist.eigentlich.net>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <20230706171922.752429-1-heiko@ist.eigentlich.net>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg26831.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>