Revert "Remove redundant "std::move"s in return statements"

The build failed with

  error: call to deleted constructor of 'llvm::Error'

errors.

This reverts commit 1c2241a7936bf85aa68aef94bd40c3ba77d8ddf2.
diff --git a/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp b/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp
index de0c29f..3d97fe9 100644
--- a/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp
@@ -267,9 +267,9 @@
       new StaticLibraryDefinitionGenerator(L, std::move(ArchiveBuffer), Err));
 
   if (Err)
-    return Err;
+    return std::move(Err);
 
-  return ADG;
+  return std::move(ADG);
 }
 
 Error StaticLibraryDefinitionGenerator::tryToGenerate(