[PATCH] [libcxxabi] Remove strict dependency on llvm-config.

[Keno Fischer]

> Well, if there's an invalid llvm-config on your system, you should probably remove llvm-config :) I think I can probably just reorder the if/elseif and get the behavior you want though, but that might cause issues with rerunning cmake on an already configured directory.

It's only invalid while rebuilding libcxxabi though, it'll work again just fine after ;)

> Interesting. Outside the realm of this patch, but I'll fix that too.

Thanks!

http://reviews.llvm.org/D5016