Meta: Add test262-runner to the GN build

Meta/gn/secondary/Tests/LibJS/BUILD.gn

@@ -10,7 +10,20 @@ unittest("test-js") {
   ]
 }
 
-group("LibJS") {
-  deps = [ ":test-js" ]
-  testonly = true
+executable("test262-runner") {
+  sources = [ "test262-runner.cpp" ]
+  include_dirs = [ "//Userland/Libraries" ]
+  deps = [
+    "//AK",
+    "//Userland/Libraries/LibCore",
+    "//Userland/Libraries/LibJS",
+  ]
+}
+
+group("LibJS") {
+  testonly = true
+  deps = [
+    ":test-js",
+    ":test262-runner",
+  ]
 }