I just did an update and build for the first time since around Dec 20,
and received an error about unresolved references to
__assert13(). Looking through the mailing list archives, I found a
message saying that I needed to rebuild and install libc before doing
the full build, so I tried that. It failed because it couldn't find
libc.so.12.70, so I did a make clean (followed by a cvs update) in the
libc directory, then tried another make. Now it's giving the following
complaint:

  make: don't know how to make /drive2/src/src/lib/libc/stdlib/multibyte.c. Stop

The odd thing about this is that multibyte.c is in libc/locale, not
libc/stdlib.

How can I get myself out of this mess and back to building everything?