the target is now(?) prefixed with Geant4:: otherwise we get a linking error

We no longer test with ROOT 6.22, and in 6.32 PyROOT is coming back but subtly fails on macOS

I hope this will work fine. If the list of headers or linkdefs changes, then cmake should re-run anyway and that will call the file(Generate) to recreate the script, and if only the file content of headers or linkdefs changes, we only have to re-run the shell script.

because add_custom_command does not know the COMPILE_LANGUAGE we are not allowed to treat definitions with that genex inside.
We cannot use add_custom_command(TARGET because that fails with the same error, even though it maybe shouldn't

For compatibility with ninja(?) we need to use these $<CONFIG>$<COMPILE_LANGUAGE> shenanigans

add USE_COMMAND_FOR_GENERATION to fall back to old way

LCIO now exports LCIO::lcio, so we could use that if LCIO is new enough

DD4hepBuild: add -Wno-psabi to compiler flags to ignore warnings about ABI changes that we will never have issues with

As it stands, this project requires to find a python version matching
the one ROOT was build against EXACTLY. This has been discussed in #842.
This adds an option `DD4HEP_RELAX_PYVER` that will accept **any** python
version. It will then perform a custom check if major and minor version
of the ROOT python version and the one found match (in which it should
be safe to assume ABI compatibility). If not, it prints a warning but
continues with the build.

 - including necessary build macro etc

This reverts commit bea8748c.

Add examples of specialized shape views for CMS.
Simplyfiy grammar handling.

There was a bug in the dd4hep_add_test_reg function which was only taking into account the last dependency of a test when several were present.
On the way, dropped a double dependency in DDDB_clean_LONGTEST

also drop deprecated rootcling options

CMake: behave as before if BUILD_SHARED_LIBS is not defined. Needed for examples and DD4hep external packageS