Migrate `tools/bazel.rc` to `.bazelrc`

Since: [1] Bazel changed the list of resource file locations.
Adapt to that list and move `%workspace%/tools/bazelrc` to
`%workspace%/.bazelrc`. See: [2], [3] for more details.

[1] https://github.com/bazelbuild/bazel/commit/ec83598
[2] https://github.com/bazelbuild/bazel/issues/4502
[3] https://github.com/bazelbuild/bazel/issues/5756

Change-Id: Ia13c71bcff7036e2f5541618b28713d9b0d77040
diff --git a/tools/bazel.rc b/.bazelrc
similarity index 100%
rename from tools/bazel.rc
rename to .bazelrc