Fix tools/BUILD.bazel to make 'bazel cquery ...' work

ibazel (https://github.com/bazelbuild/bazel-watcher/) is running
`bazel cquery ...` which failed when there are executable targets in the
deps attribute of a go_library. This was never checked in CI because of
the manual tag of the tools target.

tools/BUILD.bazel

@@ -1,14 +1 @@
-load("@rules_go//go:def.bzl", "go_library")
-
-go_library(
-    name = "tools",
-    srcs = ["deps.go"],
-    importpath = "github.com/buildbarn/bb-clientd/tools",
-    tags = ["manual"],
-    visibility = ["//visibility:public"],
-    deps = [
-        "@cc_mvdan_gofumpt//:gofumpt",
-        "@com_github_bazelbuild_buildtools//buildifier",
-        "@org_golang_x_lint//:lint",
-    ],
-)
+# gazelle:ignore