Add missing bug number to TODO in `build/apex/art_apex_test.py`.

Test: n/a
Bug: 123602136
Change-Id: I0a03a2a8f8ad233358139f11df585875b81ac097
diff --git a/build/apex/art_apex_test.py b/build/apex/art_apex_test.py
index 97c7f61..9e4f46a 100755
--- a/build/apex/art_apex_test.py
+++ b/build/apex/art_apex_test.py
@@ -307,8 +307,8 @@
     # This is needed because the list of build targets is not propagated
     # to this script.
     #
-    # TODO: Pass build target information to this script and fix all places
-    # where this function in used (or similar workarounds).
+    # TODO(b/123602136): Pass build target information to this script and fix
+    # all places where this function in used (or similar workarounds).
     dirs = []
     for arch in ARCHS:
       dir = '%s/%s' % (path, arch)