Show config.visibility in `gn desc`

Can now enter:
`gn desc <out_dir> <label or pattern> visibility`
The result is as expected.

Change-Id: I6dcade587a3a15247829969e1d0f610ccfbfb844
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/10120
Commit-Queue: Brett Wilson <brettw@chromium.org>
Reviewed-by: Brett Wilson <brettw@chromium.org>

src/gn/desc_builder.cc

diff --git a/src/gn/desc_builder.cc b/src/gn/desc_builder.cc
index d8639b1..9dd9d5f 100644
--- a/src/gn/desc_builder.cc
+++ b/src/gn/desc_builder.cc
@@ -254,6 +254,11 @@
       res->SetWithoutPathExpansion(variables::kConfigs, std::move(configs));
     }
 
+    if (what(variables::kVisibility)) {
+      res->SetWithoutPathExpansion(variables::kVisibility,
+                                   config_->visibility().AsValue());
+    }
+
 #define CONFIG_VALUE_ARRAY_HANDLER(name, type)                        \
   if (what(#name)) {                                                  \
     ValuePtr ptr =                                                    \