GYP: prevent code generator from being directly added to All.

mojo/public/tools/bindings/mojom_bindings_generator_explicit.gypi

Index: mojo/public/tools/bindings/mojom_bindings_generator_explicit.gypi
diff --git a/mojo/public/tools/bindings/mojom_bindings_generator_explicit.gypi b/mojo/public/tools/bindings/mojom_bindings_generator_explicit.gypi
index 512e22fe1e8a4e591afab510d4cdb2af226f4259..52b24522e2d05189102d59e04ffda65959855c2a 100644
--- a/mojo/public/tools/bindings/mojom_bindings_generator_explicit.gypi
+++ b/mojo/public/tools/bindings/mojom_bindings_generator_explicit.gypi
@@ -45,6 +45,10 @@
       'message': 'Generating Mojo bindings from <@(mojom_files)',
     }
   ],
+  # Prevent the generated sources from being injected into the "all" target by
+  # preventing the code generator from being directly depended on by the "all"
+  # target.
+  'suppress_wildcard': '1',
   'direct_dependent_settings': {
     # A target directly depending on this action will compile the generated
     # sources.