Move metadata object generation for dylibs to the linker code

This deduplicates some code between codegen backends and may in the
future allow adding extra metadata that is only known at link time.

compiler/rustc_codegen_llvm/src/lib.rs

@@ -341,16 +341,11 @@ impl CodegenBackend for LlvmCodegenBackend {
         target_config(sess)
     }
 
-    fn codegen_crate<'tcx>(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        metadata: Option<&EncodedMetadata>,
-    ) -> Box<dyn Any> {
+    fn codegen_crate<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Box<dyn Any> {
         Box::new(rustc_codegen_ssa::base::codegen_crate(
             LlvmCodegenBackend(()),
             tcx,
             crate::llvm_util::target_cpu(tcx.sess).to_string(),
-            metadata,
         ))
     }