evcxr: flip back from mold to mold-unwrapped

With recent default change of `mold` to wrappper
`evcxr` started failing as:

```
$ echo 42 | nix run -f. evcxr
Welcome to evcxr. For help, type :help
Error: Compilation failed, but no parsable errors were found. STDERR:
mold: fatal: unknown command line option: -run

STDOUT:

```

The change fixes `evcxr` for me:

```
$ echo 42 | nix run -f. evcxr
Welcome to evcxr. For help, type :help
42
```

pkgs/by-name/ev/evcxr/package.nix

@@ -9,7 +9,7 @@
   libiconv,
   cargo,
   gcc,
-  mold,
+  mold-unwrapped,
   rustc,
   nix-update-script,
 
@@ -75,7 +75,7 @@ rustPlatform.buildRustPackage (finalAttrs: {
                 gcc
                 rustc
               ]
-              ++ lib.optional withMold mold
+              ++ lib.optional withMold mold-unwrapped
             )
           } \
           --set-default RUST_SRC_PATH "$RUST_SRC_PATH"