Build reflection dictionary
Created by: pieterdavid
This should build the reflection dictionary, such that it does not need to be constructed from the headers, e.g.
from cppyy import gbl
gbl.gSystem.AddDynamicPath("../test-install/lib")
gbl.gSystem.Load("libCMSJMECalculatorsDict.so")
calc = gbl.Type1METVariationsCalculator()
I enabled it only for cmake builds outside scikit-build for now
CC @sroychow