What's the reasoning behind using ld64 for gccXX?

[Sean Farley]

> The main reason that it wasn't that way was because for quite some time the rest of the toolchain was just not as well maintained.  That's no longer the case, so now we can benefit from that work in other ports.  YAY!
>
> Benefit 1 - Consistency across similar ports
> clang-mp-* use MacPorts's ld64 to link.
> apple-gcc-4.2 uses MacPorts ld64 to link and MacPorts cctools to assemble if they're installed (they're not a dependency because it would set up a dependency cycle)
> gcc-mp-* should join the party.

Should? Why? They have been working perfectly fine, and if I recall
correctly, there was a problem using ld64 with gcc 4.6 (but that could
have due to other options such as --dynamic-strings)

> Benefit 2 - MacPorts philosophy
> This helps isolate bugs due to different versions of XCode being installed in the same way we like to isolate bugs across OS version deltas by providing as much of the library stack as possible.

Please show a list of bugs this fixes.

> Benefit 3 - Required on older OSs
> On older OS versions which don't support newer XCode, they need newer versions of cctools and ld64 to even use recent compilers.

Which can easily be tested for. I figure, based on your recent
commits, that you already have these ports installed but for most
users this adds a ton of new ports that are really unnecessary.
/usr/bin/ar and friends have been working fine, and more importantly,
it's what the testers of gcc use.