Require GNU make to build binutils-gdb

[Nick Clifton]

Hi Simon,

> In gdb/, we are now making use of GNU make-specific features
> (in particular, pattern rules), so we now require building 
> with GNU make.

> For simplicity and consistency, we were wondering if we should 
> adopt the same policy for the whole binutils-gdb tree.

I think that this is a good idea, although maybe it would be 
helpful to take a two stage approach: for one release (of
binutils) issue an error message if a non-GNU make is used,
but allow a configure option to override this.  (In the same 
way that obsolete targets are currently handled).  Then for 
the release after that make GNU make a hard requirement.

That way we give users a chance to give us feedback if they
are using a non-GNU make and they do not have the option of
changing.

Cheers
  Nick