Properly define v8_enable_inspector and its override in GN.

gni/isolate.gni

 # Copyright 2016 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/sanitizers/sanitizers.gni")
-import("//build_overrides/v8.gni")
 import("//third_party/icu/config.gni")
 import("v8.gni")
 
 declare_args() {
   # Sets the test isolation mode (noop|prepare|check).
   v8_test_isolation_mode = "noop"
 }
 
 template("v8_isolate_run") {
   forward_variables_from(invoker,
@@ skipping 73 matching lines @@
       if (is_component_build) {
         component = "shared_library"
       } else {
         component = "static_library"
       }
       if (icu_use_data_file) {
         icu_use_data_file_flag = "1"
       } else {
         icu_use_data_file_flag = "0"
       }
-      if (v8_enable_inspector_override) {
+      if (v8_enable_inspector) {
         enable_inspector = "1"
       } else {
         enable_inspector = "0"
       }
       if (v8_use_external_startup_data) {
         use_external_startup_data = "1"
       } else {
         use_external_startup_data = "0"
       }
       if (v8_use_snapshot) {
@@ skipping 74 matching lines @@
         ]
       } else {
         args += [
           "--config-variable",
           "msvs_version=0",
         ]
       }
     }
   }
 }