podio, edm4hep, dd4hep: conflicts ^python +freethreading

[wdconinc]

This PR marks explicit conflicts between podio, edm4hep, and dd4hep and ^python +freethreading. To be resolved in next releases (AIDASoft/podio#911, key4hep/EDM4hep#469, AIDASoft/DD4hep#1547).

[Copilot]

Pull request overview

This PR adds explicit conflicts between the podio and edm4hep packages and Python with free-threading enabled (^python +freethreading). These conflicts prevent incompatible combinations until future releases of these packages add support for Python free-threading.

• Adds conflict declaration for podio@:1.6 with ^python +freethreading, requiring version 1.7 or later
• Adds conflict declaration for edm4hep@:0.99.4 with ^python +freethreading, requiring version 0.99.5 or later

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
repos/spack_repo/builtin/packages/podio/package.py	Adds conflict preventing podio versions up to 1.6 from being used with Python free-threading
repos/spack_repo/builtin/packages/edm4hep/package.py	Adds conflict preventing edm4hep versions up to 0.99.4 from being used with Python free-threading

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[tmadlener]

This comes a bit too late for now, but I think all the conflicts could be removed and replaced by explicitly injecting the python prefix via cmake, all the packages have corresponding cmake variables that should allow for this

-podio_PYTHON_INSTALLDIR

• EDM4HEP_PYTHON_INSTALLDIR
• DD4HEP_PYTHON_INSTALL_DIR

All of them are populated to some more (or less as we have seen) reasonable default, but they can all be either specified as relative (to the CMAKE_INSTALL_PREFIX) or absolute paths and the corresponding python files will end up there.

[wdconinc]

This comes a bit too late for now, but I think all the conflicts could be removed and replaced by explicitly injecting the python prefix via cmake, all the packages have corresponding cmake variables that should allow for this

-podio_PYTHON_INSTALLDIR

• EDM4HEP_PYTHON_INSTALLDIR
• DD4HEP_PYTHON_INSTALL_DIR

All of them are populated to some more (or less as we have seen) reasonable default, but they can all be either specified as relative (to the CMAKE_INSTALL_PREFIX) or absolute paths and the corresponding python files will end up there.

True, but determining the target directory from spack is not trivial either and requires spinning up a subprocess of the target python (since the python being used by spack itself is not the relevant one). That complexity is avoided with a conflict that only restricts until the next versions are released.