Fixed compiler error

Author: ndrewxie

tests/run-make-fulldeps/hotplug_codegen_backend/the_backend.rs

@@ -15,7 +15,7 @@ extern crate rustc_target;
 
 use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_codegen_ssa::{CodegenResults, CrateInfo};
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_errors::ErrorGuaranteed;
 use rustc_metadata::EncodedMetadata;
 use rustc_middle::dep_graph::{WorkProduct, WorkProductId};
@@ -49,11 +49,11 @@ impl CodegenBackend for TheBackend {
         ongoing_codegen: Box<dyn Any>,
         _sess: &Session,
         _outputs: &OutputFilenames,
-    ) -> Result<(CodegenResults, FxHashMap<WorkProductId, WorkProduct>), ErrorGuaranteed> {
+    ) -> Result<(CodegenResults, FxIndexMap<WorkProductId, WorkProduct>), ErrorGuaranteed> {
         let codegen_results = ongoing_codegen
             .downcast::<CodegenResults>()
             .expect("in join_codegen: ongoing_codegen is not a CodegenResults");
-        Ok((*codegen_results, FxHashMap::default()))
+        Ok((*codegen_results, FxIndexMap::default()))
     }
 
     fn link(