attempting to point the relative destination with "--install-data" does not seem to have an effect. the specified directory is created, but resources are still installed relative to the present working directory.

setup.cfg:

[files]
resources =
    externalfiles/tobemoved.txt = support


% pysetup3 run install_dist --install-data /tmp/example


/tmp/example is created with no files, ./support/tobemoved.txt is created

This is one of the things that were left under-specified when the resources subsystem was introduced by adding working code instead of a PEP.  I think that --install-data is obsolete now, and that there should be another way to override specific sysconfig variables or paths (which are used to install data files/resources) from the command line and config files, to replace --install-data.