Use -I, -D, -U passed to rootcling also for rootcling-with-TCling.

Must delay the parsing of the Linkdef files until the -I have been added to TCling.
Apply change from master.
Review: dictionary contain only STL classes and thus no root pcm files.
Move METAOLLVM into ROOTCLINGEXEEXTRAO (review).
Silence compiler warning (review).
Do not #define gInterpreterClassDef for rootcling.