Target oldest supported OS by default

[Walter Bright]

On 1/10/2013 12:24 PM, Jacob Carlborg wrote:
> I just had an issue with a binary compiled on Mac OS X 10.8 not running on any
> older version. When I found the problem it was an easy fix adding the following
> linker flags:
>
> -L-macosx_version_min -L10.6
>
> Would it be a good idea if DMD targeted the oldest supported OS by default, that
> is, when invoking GCC to link?
>

Presumably there is some reason why this is not the default behavior of the 
linker. Some performance problem, maybe?