Mock rules_shell.

Bug: 372860136
Change-Id: I99b6830a548b13de3f22ffc12463bf52b33a895c
diff --git a/gbl/bazel.MODULE.bazel b/gbl/bazel.MODULE.bazel
index 04fd560..852d16b 100644
--- a/gbl/bazel.MODULE.bazel
+++ b/gbl/bazel.MODULE.bazel
@@ -95,6 +95,11 @@
 )
 
 local_path_override(
+    module_name = "rules_shell",
+    path = "external/bazelbuild-rules_shell",
+)
+
+local_path_override(
     module_name = "protobuf",
     path = "bootable/libbootloader/gbl/fake_modules/protobuf",
 )