rules_cc: Add top-level BUILD file to distribution.

Before this commit Bazel could not use the distribution since it failed with "Every .bzl file must have a corresponding package, but '@rules_cc//:internal_deps.bzl' does not have one."

https://buildkite.com/bazel/bazel-federation-distro-pre-release-testing/builds/20#29164fc9-b0bb-41aa-b62f-e2f3f20e9efc

PiperOrigin-RevId: 275263945
Change-Id: I12216f2070ddc579f553a22975790bbc9a18f0f9

BUILD

diff --git a/BUILD b/BUILD
index 7ba8a85..5e0fc3a 100644
--- a/BUILD
+++ b/BUILD
@@ -7,6 +7,7 @@
 filegroup(
     name = "distribution",
     srcs = [
+        "BUILD",
         "LICENSE",
         "internal_deps.bzl",
         "internal_setup.bzl",