Fix missing print command in a GN error case.

This mistake resulted in the error never getting reported.

Review URL: https://codereview.chromium.org/1144103004

Cr-Original-Commit-Position: refs/heads/master@{#331182}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 81d969a7fef4a51875a770e051780192a1903db6

tools/gn/commands.cc

diff --git a/tools/gn/commands.cc b/tools/gn/commands.cc
index b09a74e..556f75f 100644
--- a/tools/gn/commands.cc
+++ b/tools/gn/commands.cc
@@ -397,7 +397,7 @@
     Err(Location(), "Not a target.",
         "The \"" + label.GetUserVisibleName(false) + "\" thing\n"
         "is not a target. Somebody should probably implement this command for "
-        "other\nitem types.");
+        "other\nitem types.").PrintToStdout();
     return nullptr;
   }