Dynamically link if any deps use dynamic libs

[cbvi]

This lets a pure myrddin project use an installed lib that binds to C and be linked correctly.

I think addlib is the best place to determine this since it's walking the dependency tree anyway, but maybe there's a better way?

[cbvi]

How about this?

[cbvi]

Third time's the charm?

It's back in the myrtag, so not b.dynlink, because of multiple targets as you explained earlier.

[oridb]

Looks good to me.