munix: add -- before command args to prevent option parsing

muvm was interpreting command arguments like '-c' (from /bin/sh -c)
as its own options. Adding '--' separates muvm options from the
command and its arguments.

munix

@@ -205,5 +205,5 @@ bwrap --unshare-all --share-net \
     -e container=munix \
     -e MICROVM_CLOSURE="$MICROVM_CLOSURE" \
     -e MICROVM_UID="$MICROVM_UID" -e MICROVM_GID="$MICROVM_GID" \
-    -i -t "${MICROVM_COMMAND[@]}" \
+    -i -t -- "${MICROVM_COMMAND[@]}" \
   13< /etc/resolv.conf