Collapse all uses of target.options.foo into target.foo

with an eye on merging `TargetOptions` into `Target`.

`TargetOptions` as a separate structure is mostly an implementation detail of `Target` construction, all its fields logically belong to `Target` and available from `Target` through `Deref` impls.

compiler/rustc_codegen_llvm/src/back/archive.rs

@@ -206,7 +206,7 @@ impl<'a> LlvmArchiveBuilder<'a> {
     }
 
     fn llvm_archive_kind(&self) -> Result<ArchiveKind, &str> {
-        let kind = &*self.config.sess.target.options.archive_format;
+        let kind = &*self.config.sess.target.archive_format;
         kind.parse().map_err(|_| kind)
     }