Making MacPorts Think A Dependency Is Already Installed
No, this is not supported by any standard way. The maintainers of MacPorts care a lot about reproducibility of the builds and thus, MacPorts does not allow any other software to fulfil the requirement.

These entries in the MacPorts FAQ should answer this question in more detail:


Will MacPorts link to system libraries rather than its own?
Why is MacPorts using its own libraries?