[Bazel] Add examples to bazelignore

This avoids Bazel recursing into these directories when overlayed, which
will break if someone has run Bazel in these dirs (which would only be
successful with the http_archive example) because of the Bazel directory
symlinks (already gitignored).

Reviewed By: jpienaar

Differential Revision: https://reviews.llvm.org/D105357

utils/bazel/.bazelignore

@@ -1 +1,2 @@
 llvm-project-overlay
+examples