The internal "completionCallback" and "listPossibleCallback" helpers
are used only when building with editline; hence, do not build then
when using readline, matching their usage in
"ReadlineLikeInteracter::init()".
... as well as match buildReadlineNoMarkdown.
Unfortunately it doesn't support long inputs or multiline inputs
for now.
This needs to make better use of the interacter interface.
At this point many features are stripped out, but this works:
- Can run libnix{util,store,expr} unit tests
- Can run some Nix commands
Co-Authored-By volth <volth@volth.com>
Co-Authored-By Brian McKenna <brian@brianmckenna.org>
