ASDF Issue with compiler warnings on ABCL

[Robert Goldman]

ASDF wraps its compilation process with WITH-COMPILATION-UNIT.

On at least some implementations, this is necessary so that building
doesn't emit spurious undefined function (variable, etc.) warnings.

However, on ABCL, using WITH-COMPILATION-UNIT has the side effect of
causing warnings to be intercepted and handled by HANDLE-WARNING.  Then
it seems that *resignal-compiler-warnings* is bound to NIL, and the
compiler swallows them, instead of allowing them to flow down the stack
to ASDF's handlers.

In turn, this causes at least some of our regression tests to fail,
because they check for expected warnings.

This looks to me like a bug, but perhaps it's a feature ;-)  Would you
please explain and let us know how to handle this?

thanks,
r