Hi Mark,
Thanks for filing that in Trac. I've discovered a work-around. ASDF3 lets me do this:
(asdf:operate 'asdf:monolithic-compile-bundle-op "mysystem")
to produce mysystem--all-systems.abcl somewhere under ~/.cache/...
This file has no sources and can be loaded in with #'load .
https://www.common-lisp.net/project/asdf/asdf.html#Predefined-operations-of-...
Vibhu