rustc: Remove dylib crate type from most rustc crates

Now that procedural macros no longer link transitively to libsyntax,
this shouldn't be needed any more! This commit is an experiment in
removing all dynamic libraries from rustc except for librustc_driver
itself. Let's see how far we can get with that!

src/librustc_codegen_llvm/lib.rs

@@ -39,6 +39,7 @@ extern crate rustc_incremental;
 extern crate rustc_codegen_utils;
 extern crate rustc_codegen_ssa;
 extern crate rustc_fs_util;
+extern crate rustc_driver as _;
 
 #[macro_use] extern crate log;
 #[macro_use] extern crate syntax;