Add testonly flag to GN

tools/gn/config_values_extractors_unittest.cc

Index: tools/gn/config_values_extractors_unittest.cc
diff --git a/tools/gn/config_values_extractors_unittest.cc b/tools/gn/config_values_extractors_unittest.cc
index a4082265cebb94bfd98fc835465dfbd8ccf659a2..b0c65cafd28bfd754f613b7d161f83c09c02fe0f 100644
--- a/tools/gn/config_values_extractors_unittest.cc
+++ b/tools/gn/config_values_extractors_unittest.cc
@@ -28,6 +28,7 @@ struct IncludeWriter {
 
 TEST(ConfigValuesExtractors, IncludeOrdering) {
   TestWithScope setup;
+  Err err;
 
   // Construct a chain of dependencies: target -> dep1 -> dep2
   // Add representative values: cflags (opaque, always copied) and include_dirs
@@ -100,9 +101,9 @@ TEST(ConfigValuesExtractors, IncludeOrdering) {
       SourceDir("//target/"));
 
   // Mark targets resolved. This should push dependent configs.
-  dep2.OnResolved();
-  dep1.OnResolved();
-  target.OnResolved();
+  ASSERT_TRUE(dep2.OnResolved(&err));
+  ASSERT_TRUE(dep1.OnResolved(&err));
+  ASSERT_TRUE(target.OnResolved(&err));
 
   // Verify cflags by serializing.
   std::ostringstream flag_out;