tools: add --error-on-warn configure flag in test-shared.yml

Given that this workflow compiles V8 and other libs separately, that
would allow us to detect any Node.js-specific warning that needs to be
addressed.

Signed-off-by: Antoine du Hamel <duhamelantoine1995@gmail.com>
PR-URL: #66751
Reviewed-By: Filip Skokan <panva.ip@gmail.com>

Author: aduh95

tools/nix/ci-shell.nix

@@ -9,6 +9,10 @@ args@{
     loadJSBuiltinsDynamically = false;
     devTools = [ ];
     benchmarkTools = [ ];
+    extraConfigFlags = [
+      "--debug-node"
+      "--error-on-warn"
+    ];
   }
   // pkgs.lib.optionalAttrs pkgs.stdenv.hostPlatform.isDarwin (
     # Disable optional features on Darwin for coverage and faster CI.
@@ -20,6 +24,7 @@ args@{
     // {
       withSSL = true; # no-SSL coverage is ensured by Jenkins
       extraConfigFlags = [
+        "--error-on-warn"
         "--without-inspector"
         "--without-node-options"
       ];