Building for more than one host architecture

[jba@aps.anl.gov (Janet B. Anderson)]

In answer to the following comment

> If you are trying to get rid of the tools directory altogether, where
> do you put something like my HostArch script? It is needed very early
> on in the make procedure. It could be incorporated in the makefiles,
> but it would be a bit messy, and it is useful outside of make.

I thought that the HostArch script could be used by all developers of 
base, extensions, and applications at login time to define the HOST_ARCH
environment variable. HOST_ARCH would then come from the environment for
all builds of base and extensions application directories. I also thought
that we would use Rozelle Wright's suggestion that all startup files be
distributed with epics, and so I thought we could put them all together
in a new startup directory within the epics tree.

Janet