[inspector] Build inspector under v8_enable_inspector build flag.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index a7742f37e6981334c7c5fc68549b9aca17d8311e..9d25f2fd62dc24afe9812bbcbfe19be5bd537a14 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -140,6 +140,9 @@ config("external_config") {
     ]
   }
   include_dirs = [ "include" ]
+  if (v8_enable_inspector_override) {
+    include_dirs += [ "$target_gen_dir/include" ]
+  }
   libs = []
   if (is_android && current_toolchain != host_toolchain) {
     libs += [ "log" ]
@@ -2016,6 +2019,10 @@ v8_source_set("v8_base") {
     sources += [ "$target_gen_dir/debug-support.cc" ]
     deps += [ ":postmortem-metadata" ]
   }
+
+  if (v8_enable_inspector_override) {
+    deps += [ "src/inspector:inspector" ]
+  }
 }
 
 v8_source_set("v8_libbase") {