GN: Make file/dir resolving return errors.

tools/gn/commands.cc

Index: tools/gn/commands.cc
diff --git a/tools/gn/commands.cc b/tools/gn/commands.cc
index 556f75f721bbe4d2a5e0becf4a9dd43c9ef0b88e..ab22ebe43c8851b799c8d899404c199567781442 100644
--- a/tools/gn/commands.cc
+++ b/tools/gn/commands.cc
@@ -90,8 +90,13 @@ bool ResolveStringFromCommandLineInput(
                                Value(nullptr, input), &err);
   if (err.has_error()) {
     // Not a valid label, assume this must be a file.
+    err = Err();
     file_matches->push_back(current_dir.ResolveRelativeFile(
-        input, setup->build_settings().root_path_utf8()));
+        Value(nullptr, input), &err, setup->build_settings().root_path_utf8()));
+    if (err.has_error()) {
+      err.PrintToStdout();
+      return false;
+    }
     return true;
   }
 
@@ -106,7 +111,11 @@ bool ResolveStringFromCommandLineInput(
   } else {
     // Not an item, assume this must be a file.
     file_matches->push_back(current_dir.ResolveRelativeFile(
-        input, setup->build_settings().root_path_utf8()));
+        Value(nullptr, input), &err, setup->build_settings().root_path_utf8()));
+    if (err.has_error()) {
+      err.PrintToStdout();
+      return false;
+    }
   }
 
   return true;