Dropping recommendation to install system headers / command line tools

[Ryan Schmidt]

On Jul 3, 2017, at 23:21, Jeremy Huddleston Sequoia wrote:

> base currently outputs a warning if system headers are not installed.  I modified the warning a few months ago when I improved our support for building against SDKs, and it now reads:
> 
>   Warning: System headers do not appear to be installed. Most ports should build corectly, but if you experience problems due to a port depending on system headers, please file a ticket at https://trac.macports.org.
>   Warning: You can install them as part of the Xcode Command Line Tools package by running `xcode-select --install'.
> 
> How many developers are using Xcode with the system headers installed vs without system headers?  If you are using system headers (currently installed through the CLTools package and through similar means on older OS versions), can you please indicate why you are unable to use an SDK?  I haven't seen any tickets about issues when using an SDK over system headers, and the only issue I'm aware of is with gcc ports (which is an upstream bug and mostly worked around).
> 
> I'd like to remove this warning in order to indicate that building against an SDK is now a more supported configuration.  IMO, it should be the *preferred* configuration as it avoids /usr/local/{include,lib} contamination.  What are the thoughts on this?

Last I checked, graphite2 would not build if CLTools were not installed:

https://trac.macports.org/ticket/49325

I don't know how many other ports are in the same situation.