deno: Build rusty-v8 on big-parallel

After the switch to building rusty-v8 from source and some hiccups with
test failures on Hydra, we have recurring timeouts on Hydra.

rusty-v8 is mostly busy compiling c/c++ code. That is highly
parallelizable, and that part is without any log output.
The solution against the timeouts and to speed things up is to build
rusty-v8 on big-parallel.

Builds on an older 32-core Intel CPU take 30 minutes, builds on the
default Hydra dual-core environments apparently and logically take
easily more than three hours.

pkgs/by-name/de/deno/librusty_v8.nix

@@ -159,6 +159,8 @@ rustPlatform.buildRustPackage (finalAttrs: {
     runHook postInstall
   '';
 
+  requiredSystemFeatures = [ "big-parallel" ];
+
   meta = {
     description = "Rust bindings for the V8 JavaScript engine";
     homepage = "https://github.com/denoland/rusty_v8";