In principle the BDT representation used by MVAutils does no depend on TMVA.
TMVA is needed for "converting" between formats.
Move out the relevant code from the BDT class itself to a helper.
@akraszna explained to me that we use
--as-needed when linking, so by not using anything that depends on TMVA
on what is compiled for the library the TMVA should not be part of its dependencies.
To confirm I also checked the .so of the MVAUtils library via
ldd and I do not see TMVA.
I see it for the executable under utils (for which the TMVA/XML/MathCore are needed).
Also removed some of the ROOT dependencies that seemed unneeded.