build_arch vs. configure.build_arch

[Bryan Blackburn]

On Sun, Sep 06, 2009 at 07:48:32AM -0500, Ryan Schmidt said:
> What is the difference between build_arch and configure.build_arch?
> Which should we compare against in Portfiles when we want to know?
> Which should we set when we want to force the build one way or
> another?

configure.build_arch defaults to whatever build_arch is:

<http://trac.macports.org/browser/trunk/base/src/port1.0/portconfigure.tcl#L154>

> 
> Is there an easy way to say "this port doesn't support 64-bit" or do
> we have to do the "if x86_64 is requested then use i386 else if ppc64
> is requested then use ppc" dance?

The problem with this is, what do we do about dependencies?  If port B
depends on A, and A was built 64bit but B says "I only do 32bit", then what?

Bryan