[gentoo-alt] Gentoo Prefix on OSX now uses Clang

[Fabian Groffen]

As the subject says, a bootstrap on OSX will now work itself into a
system with Clang as the only and main compiler.  This also means that
bootstrapping finally works normally again on OSX 10.9 Maverick and
10.10 Yosemite.  Long overdue.  Too long, probably.

If you have an existing prefix, it will likely try to install clang.  If
you want to keep your Prefix, you probably have to first manually
install clang/llvm-3.4 before you can compile 3.5.  I haven't tested
this, sorry.

This switch would not have been possible without the hard work of many
non-devs that contributed patches and fixes over the years to
binutils-apple and llvm.  Many thanks to you all!

For the curious, https://bugs.gentoo.org/show_bug.cgi?id=538366
documents more or less what a bootstrap now does.  I decided not to try
and skip the clang-3.4 step (although we can on newer systems) because
then I'd know it would work on older systems the same way.  In the end
on a modern machine, it just takes a while, but I was able to do do
three full bootstraps on a single rainy day (with some stops inbetween)
on my rusty Core i7 iMac.  It shouldn't be so bad.  It took me an hour
or so on a Mac Mini Core i5 with an SSD this morning.  So I hope it's ok
for people to (finally) re-bootstrap their prefixes.

Fabian

-- 
Fabian Groffen
Gentoo on a different level