Add --disable-fd-passing option.

.. and enable for the minix3 test VM.  This will cause it to more reliably
skip tests that need FD passing and should fix the current test breakage.

.github/configs

@@ -269,20 +269,22 @@ case "${TARGET_HOST}" in
 	;;
     minix3)
 	CONFIGFLAGS="${CONFIGFLAGS} --disable-security-key"
+	# Unix domain sockets don't work quite like we expect, so also
+	# disable FD passing (and thus multiplexing).
+	CONFIGFLAGS="${CONFIGFLAGS} --disable-fd-passing"
 	LIBCRYPTOFLAGS="--without-openssl"
+
 	# Minix does not have a loopback interface so we have to skip any
 	# test that relies on one.
 	# Also, Minix seems to be very limited in the number of select()
 	# calls that can be operating concurrently, so prune additional tests for that.
 	T="addrmatch agent-restrict brokenkeys cfgmatch cfgmatchlisten cfgparse
-	    connect connect-uri exit-status forwarding hostkey-agent
-	    key-options keyscan knownhosts-command login-timeout
+	    connect connect-uri dynamic-forward exit-status forwarding
+	    forward-control
+	    hostkey-agent key-options keyscan knownhosts-command login-timeout
 	    reconfigure reexec rekey scp scp-uri scp3 sftp sftp-badcmds
 	    sftp-batch sftp-cmds sftp-glob sftp-perm sftp-uri stderr-data
 	    transfer"
-	# Unix domain sockets don't work quite like we expect, so also skip any tests
-	# that use multiplexing.
-	T="$T connection-timeout dynamic-forward forward-control multiplex"
 	SKIP_LTESTS="$(echo $T)"
 	TEST_TARGET=t-exec
 	SUDO=""

configure.ac

@@ -5305,6 +5305,16 @@ AC_DEFINE_UNQUOTED([_PATH_SSH_PIDDIR], ["$piddir"],
 	[Specify location of ssh.pid])
 AC_SUBST([piddir])
 
+
+AC_ARG_ENABLE([fd-passing],
+	[  --disable-fd-passing    disable file descriptor passsing [no]],
+	[
+		if test "x$enableval" = "xno" ; then
+			AC_DEFINE([DISABLE_FD_PASSING])
+		fi
+	]
+)
+
 dnl allow user to disable some login recording features
 AC_ARG_ENABLE([lastlog],
 	[  --disable-lastlog       disable use of lastlog even if detected [no]],