clang 3.4 can't be configured (part of a selfupdate)

[Lawrence Velázquez]

> On Jul 29, 2016, at 4:05 PM, Ken Cunningham
> <ken.cunningham.webuse at gmail.com> wrote:
> 
> I believe macports automatically sets build_arch to the proper value
> depending on your hardware <https://support.apple.com/en-ca/HT201948>.
> 
> <https://guide.macports.org/chunked/internals.configuration-files.html>
> 
> Don't forget, in macports.conf, the commented out values are actually
> the default values being used, they are not really ignored.

This is true in general, but for build_arch the commented-out "i386" is
a placeholder. The method used to dynamically choose its default is
explained in the preceding comment.

vq