Rollup merge of #145894 - zetanumbers:issue-142949, r=WaffleLapkin

Ensure the coordinator thread terminates before its channels drop

Fixes #142949

Explanation: #142949 (comment)

Author: jhpratt

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -1957,10 +1957,13 @@ impl<B: ExtraBackendMethods> Drop for Coordinator<B> {
 pub struct OngoingCodegen<B: ExtraBackendMethods> {
     pub backend: B,
     pub crate_info: CrateInfo,
-    pub codegen_worker_receive: Receiver<CguMessage>,
-    pub shared_emitter_main: SharedEmitterMain,
     pub output_filenames: Arc<OutputFilenames>,
+    // Field order below is intended to terminate the coordinator thread before two fields below
+    // drop and prematurely close channels used by coordinator thread. See `Coordinator`'s
+    // `Drop` implementation for more info.
     pub coordinator: Coordinator<B>,
+    pub codegen_worker_receive: Receiver<CguMessage>,
+    pub shared_emitter_main: SharedEmitterMain,
 }
 
 impl<B: ExtraBackendMethods> OngoingCodegen<B> {