rescue: Restore 'make depend' call to fix WITH_META_MODE after r334008.

The rescue/crunchgen build avoids linking binaries for the objects it is
building by doing 'make foo.o bar.o' rather than 'make all'. This breaks the
implicit 'beforebuild: depend' dependency which ensured that all source files
were generated and up-to-date before building the object files. This
manifested as a WITH_META_MODE build problem for bin/sh in the rescue build
with syntax.{c,h} not properly being regenerated or recognized as changed in
the dependency graph.

Sponsored by: Dell EMC
MFC after: 1 week
Reported by: many