If only BB_DPKG was enabled in Config.h, busybox would not build; it'd say:

If only BB_DPKG was enabled in Config.h, busybox would not build; it'd say:
  dpkg.c:18: #error It looks like you are using libc5, which does not support
  dpkg.c:19: #error tfind().  tfind() is used by busybox dpkg.
  dpkg.c:20: #error Please disable BB_DPKG.  Sorry.
This was fixed by changing the || to an && in the preprocessor.
(We've changed the logic in there too many times.)
Found using multibuild.pl.