hadrian: Make ghcWithInterpreter the universal source of truth about availability of the interpreter
We were doing some ad-hoc checks in different places in hadrian to
determine whether we supported the interprter or not. Now this check if
confined to one function, ghcWithInterpreter, and all the places which
use this information consult ghcWithInterpreter to determine what to
do.
Fixes #25533 (closed).
Edited by Matthew Pickering