Only depend on CFG_VERSION in rustc_interface

this avoids having to rebuild the whole compiler on each commit when
`omit-git-hash = false`.

compiler/rustc_interface/src/passes.rs

@@ -89,6 +89,7 @@ pub fn register_plugins<'a>(
         crate_name,
         sess.crate_types().contains(&CrateType::Executable),
         sess.opts.cg.metadata.clone(),
+        sess.cfg_version,
     );
     sess.stable_crate_id.set(stable_crate_id).expect("not yet initialized");
     rustc_incremental::prepare_session_directory(sess, crate_name, stable_crate_id)?;

compiler/rustc_interface/src/queries.rs

@@ -369,7 +369,7 @@ impl Linker {
 
         if sess.opts.unstable_opts.no_link {
             let rlink_file = self.prepare_outputs.with_extension(config::RLINK_EXT);
-            CodegenResults::serialize_rlink(&rlink_file, &codegen_results)
+            CodegenResults::serialize_rlink(sess, &rlink_file, &codegen_results)
                 .map_err(|error| sess.emit_fatal(FailedWritingFile { path: &rlink_file, error }))?;
             return Ok(());
         }

compiler/rustc_interface/src/tests.rs

@@ -52,7 +52,8 @@ fn mk_session(matches: getopts::Matches) -> (Session, CfgSpecs) {
         output_file: None,
         temps_dir,
     };
-    let sess = build_session(sessopts, io, None, registry, vec![], Default::default(), None, None);
+    let sess =
+        build_session(sessopts, io, None, registry, vec![], Default::default(), None, None, "");
     (sess, cfg)
 }
 

compiler/rustc_interface/src/util.rs

@@ -104,6 +104,7 @@ pub fn create_session(
         lint_caps,
         file_loader,
         target_override,
+        rustc_version_str().unwrap_or("unknown"),
     );
 
     codegen_backend.init(&sess);