weird (buggy?) build dependency on a clang port

[Joshua Root]

First let me point you to this recent thread: 
<https://lists.macosforge.org/pipermail/macports-dev/2016-July/033272.html>

On 2016-9-9 00:09 , René J.V. Bertin wrote:
> I can still understand (=/= agree) that the compiler selection procedure is designed to take the lowest version of a compiler that is supposed to be able to build given code.

It isn't. It is designed to use the first compiler in the fallback list 
that is available and not blacklisted. It is implicit in this that 
compilers earlier in the list are more preferable than later ones.

> But why does it not take the lowest *available* version, and why does it tell me to install (= activate) clang-3.7 rather than install clang-3.6 (from scratch)?

Because macports-clang-3.7 occurs first in the fallback list. Print out 
${compiler.fallback} if you don't believe me. :)

Installed compiler ports are not considered "more available" than 
uninstalled ones.

- Josh