src: fix compiler warning in node_worker.cc

Currently, when configuring --without-ssl the following compiler warning
is generated:
../src/node_worker.cc:192:10:
warning: unused variable 'inspector_started' [-Wunused-variable]
    bool inspector_started = false;
         ^
1 warning generated.

This commit adds a macro guard to the variable to avoid the warning.

PR-URL: #28198
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

src/node_worker.cc

@@ -189,7 +189,9 @@ void Worker::Run() {
     Locker locker(isolate_);
     Isolate::Scope isolate_scope(isolate_);
     SealHandleScope outer_seal(isolate_);
+#if NODE_USE_V8_PLATFORM && HAVE_INSPECTOR
     bool inspector_started = false;
+#endif
 
     DeleteFnPtr<Environment, FreeEnvironment> env_;
     OnScopeLeave cleanup_env([&]() {