bug#50060: The REPL does not honor --no-auto-compile

Even when guile is run with --no-auto-compile, the
REPL still seems to be compiling the source.

$ guile --no-auto-compile
GNU Guile 3.0.5.130-5a1e7
[Legalese…]
scheme@(guile-user)> unbound-variable
;;; <stdin>:1:0: warning: possibly unbound variable `unbound-variable'
[Backtrace…]

This "possibly unbound variable" warning comes from
compilation (which can be seen by putting the same
code in a script and running with or without auto-compilation).

This is annoying, because in the REPL the code
is run immediately and we don't need the warning
about a "possibly unbound variable" just before
the actual error. In fact, it would seem desirable
to make "no auto-compilation" the default for the
REPL. Code run there is typically not
performance-sensitive.

(Originally reported at 
https://lists.gnu.org/archive/html/guile-user/2021-06/msg00065.html.)