support pulley even if host triplet also works

[cpetig]

Previously executing pulley required winch or cranelift even if pulley would be available - because the host triplet was used unconditionally if possible.

[github-actions]

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[alexcrichton]

Thanks for this! I think though it might be best to ungate the condition above this for if let Some(target) perhaps? Previously that was only available with cranelift/winch because it was part of self.compiler_config, but refactoring lately has made self.target always available regardless of crate features and the cfg's haven't really caught up yet. I think that would remove the need for the addition here too?