Title	Upgrade default macOS Travis image to `xcode6.4`
Status	Accepted
Author(s)	Andreas Kloeckner <inform@tiker.net>
Created	Nov 8, 2016
Updated	Jan 8, 2016
Discussion	#6
Implementation	(listed below)

Abstract

Upgrade the default Travis image to xcode6.4.

Implementation

Adapt conda smithy so that it applies that edit on rerender. One-liner change here
Apply the change in the staged-recipes master branch. One-liner change here

PR
Rebuild all packages with this? (TBD? Opinions?)

Likely not necessary given C++ ABI Compatibility.
conda-forge-build-setup will be modified to automatically set the deployment target on OS/X builds.

As implemented in the linked PR, this requires conda-build version 2, allowing the switch to that version and this change to be implemented as part of the same process. (More discussion)

The current default image (beta-xcode6.1) is deprecated and will cease to be supported/provided by Travis, so this change will have to happen at some point anyway.

It will go away on January 21, 2017 according to the stated plan in the linked post. At that point, all packages specifying the previous image (beta-xcode6.1) will implicitly be bumped to Travis's default image, which will result in packages that do not meet conda-forge's promise of OS compatibility back to 10.9.
Multiple packages need this to move forward:
- Apache Arrow (Issues related to rpath/@loader_path)
- libdynd (Insufficient C++14 support in the current image)
- clang 3.8/3.9 (Clang compilation crashes with the current image)

The default deployment target for xcode6.4 is macOS 10.10. It would need to be forced to 10.9 (the lowest supported one for that image) by hand.
The proposed change will not drop support for any previously supported OS versions.

All CFEPs are explicitly CC0 1.0 Universal.