Revert "Remove std::env::set_current_dir() call from EngineState::merge_env()" (#12954)

Reverts nushell/nushell#12922

crates/nu-std/src/lib.rs

@@ -98,7 +98,8 @@ use std pwd
 
     eval_block::<WithoutDebug>(engine_state, &mut stack, &block, pipeline_data)?;
 
-    engine_state.merge_env(&mut stack)?;
+    let cwd = engine_state.cwd(Some(&stack))?;
+    engine_state.merge_env(&mut stack, cwd)?;
 
     Ok(())
 }