depends_build

[Mark Brethen]

When is the depends_build keyword necessary? For example, the reduce-algebra build doc has this:

GNU make (other versions of "make" are not liable to work), autoconf
      and automake. Well you can probably survive without having autoconf
      and automake, but if you have them you should use a reasonably up to
      date version.
  For CSL you need a C/C++ development context.

These are common. Is it necessary to include them in a depends_build statement?


Mark