librustllvm should be a static library

[alexcrichton]

There's no reason for librustllvm to be built as a dynamic library any more. All of the dependent LLVM libraries are all static libraries, so we should be able to slurp in all these dependencies statically.

The tough part here is that we use llvm-config to figure out the set of LLVM libraries to link to, but I think that this would require hard-coding all of them into #[link(name = "foo", kind = "static")] on the extern block in librustc/lib/llvm.rs file. I don't really see a way around this.