bug#27810: macOS runtime feature detection

[Alan Third]

On Sat, Jul 29, 2017 at 03:07:05PM -0400, Richard Stallman wrote:
>   > I’m afraid I don’t understand why it’s a problem for cross
>   > compilation. At the moment we don’t even provide any way of building
>   > Emacs on one version of macOS that is guaranteed to work on another
>   > version of macOS, never mind cross‐compiling the NS port from another
>   > platform.
> 
> Supporting cross-compilation is a general goal for GNU packages.
> That's why we make a point, in general, to use compile time
> for autoconf tests.

Should I stop working on this? I honestly don’t believe it will have
any effect on cross compilation, and the default is to not include the
feature detection code unless you ask for it explicitly.

Not including my changes makes it harder to target macOS versions
other than that of the build system.
-- 
Alan Third