remove an unnecessary as_str

Author: RalfJung

src/machine.rs

@@ -106,8 +106,7 @@ impl MemoryExtra {
     pub fn init_extern_statics<'tcx, 'mir>(
         this: &mut MiriEvalContext<'mir, 'tcx>,
     ) -> InterpResult<'tcx> {
-        let target_os = this.tcx.sess.target.target.target_os.as_str();
-        match target_os {
+        match this.tcx.sess.target.target.target_os.as_str() {
             "linux" => {
                 // "__cxa_thread_atexit_impl"
                 // This should be all-zero, pointer-sized.

src/shims/fs.rs

@@ -802,7 +802,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
         this.check_no_isolation("mkdir")?;
 
-        let _mode = if this.tcx.sess.target.target.target_os.as_str() == "macos" {
+        let _mode = if this.tcx.sess.target.target.target_os == "macos" {
             u32::from(this.read_scalar(mode_op)?.not_undef()?.to_u16()?)
         } else {
             this.read_scalar(mode_op)?.to_u32()?