emacsPackages.lspce: simplify module renaming

Actually, there is only one module on darwin systems.  So the loop is
removed.  In addition, the bash magic is replaced with nix's
stdenv.hostPlatform.extensions.sharedLibrary.

pkgs/applications/editors/emacs/elisp-packages/manual-packages/lspce/module.nix

@@ -2,8 +2,12 @@
   lib,
   fetchFromGitHub,
   rustPlatform,
+  stdenv,
 }:
 
+let
+  libExt = stdenv.hostPlatform.extensions.sharedLibrary;
+in
 rustPlatform.buildRustPackage {
   pname = "lspce-module";
   version = "1.1.0-unstable-2024-07-14";
@@ -22,13 +26,8 @@ rustPlatform.buildRustPackage {
     "--skip=msg::tests::serialize_request_with_null_params"
   ];
 
-  # rename module without changing either suffix or location
-  # use for loop because there seems to be two modules on darwin systems
-  # https://github.com/zbelial/lspce/issues/7#issue-1783708570
   postInstall = ''
-    for f in $out/lib/*; do
-      mv --verbose $f $out/lib/lspce-module.''${f##*.}
-    done
+    mv --verbose $out/lib/liblspce_module${libExt} $out/lib/lspce-module${libExt}
   '';
 
   meta = {