pw_span: Explicitly specify pw_span dependencies in GN

Bug: b/235237667
Change-Id: I856854de6d3a89510bce6912f6567c2ab86977ce
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/99620
Reviewed-by: Ted Pudlik <[email protected]>
Pigweed-Auto-Submit: Wyatt Hepler <[email protected]>
Commit-Queue: Auto-Submit <[email protected]>
diff --git a/pw_log/BUILD.gn b/pw_log/BUILD.gn
index a4499d4..3ff928e 100644
--- a/pw_log/BUILD.gn
+++ b/pw_log/BUILD.gn
@@ -85,6 +85,7 @@
     "$dir_pw_log:protos.pwpb",
     "$dir_pw_log_tokenized:metadata",
     "$dir_pw_result",
+    dir_pw_span,
   ]
   deps = [ "$dir_pw_protobuf" ]
   sources = [ "proto_utils.cc" ]