Fix missing dep for datetime_util

This should have been added in
https://fuchsia-review.googlesource.com/c/cobalt/+/648142.

Change-Id: Ia83f82c6719083dbcfeb3f3acb950cddefbe4423
Reviewed-on: https://fuchsia-review.googlesource.com/c/cobalt/+/653698
Fuchsia-Auto-Submit: Laura Peskin <pesk@google.com>
Reviewed-by: Alexandre Zani <azani@google.com>
Commit-Queue: Alexandre Zani <azani@google.com>
diff --git a/src/lib/util/BUILD.gn b/src/lib/util/BUILD.gn
index aef9756..c2f6cc8 100644
--- a/src/lib/util/BUILD.gn
+++ b/src/lib/util/BUILD.gn
@@ -95,6 +95,7 @@
     "datetime_util.h",
   ]
   configs += [ "$cobalt_root:cobalt_config" ]
+  deps = [ "$cobalt_root/src/public/lib/statusor" ]
   public_deps = [
     "$cobalt_root/src:logging",
     "$cobalt_root/src/public/lib:clock_interfaces",