hotspot: Fix Rust demangling support

Hotspot supports demangling Rust symbols using rustc-demangle. This
library is loaded at run-time since version 1.4.0. Tell the wrapper to
make it available, so that the demangling actually works.

pkgs/development/tools/analysis/hotspot/default.nix

···
     mkdir -p 3rdparty/{perfparser,PrefixTickLabels}/.git
   '';
 
+  qtWrapperArgs = [
+    "--prefix LD_LIBRARY_PATH : ${lib.makeLibraryPath [ rustc-demangle ]}"
+  ];
+
   meta = with lib; {
     description = "A GUI for Linux perf";
     longDescription = ''