Update WARNINGS.md (#1353)

* Update WARNINGS.md

Include a link to a more detailed explanation of how to handle accumulating dependencies before constructing a depset.

* Updating warnings.textproto and regenerating WARNINGS.md

---------

Co-authored-by: Tim Malmström <oreflow@google.com>
Co-authored-by: Tim Malmström <oreflow@users.noreply.github.com>

WARNINGS.md

diff --git a/WARNINGS.md b/WARNINGS.md
index 8bb24b8..90de050 100644
--- a/WARNINGS.md
+++ b/WARNINGS.md
@@ -404,6 +404,7 @@
 [understand depsets](https://docs.bazel.build/versions/main/skylark/depsets.html)
 and try to
 [reduce the number of calls to depset](https://docs.bazel.build/versions/main/skylark/performance.html#reduce-the-number-of-calls-to-depset).
+See this [explanation](https://github.com/bazelbuild/bazel/issues/5817#issuecomment-496910826) for more detail.
 
 --------------------------------------------------------------------------------
 

warn/docs/warnings.textproto

diff --git a/warn/docs/warnings.textproto b/warn/docs/warnings.textproto
index e31739a..77e572c 100644
--- a/warn/docs/warnings.textproto
+++ b/warn/docs/warnings.textproto
@@ -223,7 +223,8 @@
     "When fixing this issue, make sure you\n"
     "[understand depsets](https://docs.bazel.build/versions/main/skylark/depsets.html)\n"
     "and try to\n"
-    "[reduce the number of calls to depset](https://docs.bazel.build/versions/main/skylark/performance.html#reduce-the-number-of-calls-to-depset)."
+    "[reduce the number of calls to depset](https://docs.bazel.build/versions/main/skylark/performance.html#reduce-the-number-of-calls-to-depset).\n"
+    "See this [explanation](https://github.com/bazelbuild/bazel/issues/5817#issuecomment-496910826) for more detail."
   bazel_flag: "--incompatible_depset_union"
   bazel_flag_link: "https://github.com/bazelbuild/bazel/issues/5817"
 }