add missing license notices (#94)

toolchains/unittest/BUILD

@@ -1,5 +1,7 @@
 load("//lib:unittest.bzl", "TOOLCHAIN_TYPE", "unittest_toolchain")
 
+licenses(["notice"])
+
 toolchain_type(
     name = "toolchain_type",
     visibility = ["//visibility:public"],

workspace.bzl

@@ -1,3 +1,17 @@
+# Copyright 2019 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
 """Dependency registration helpers for repositories which need to load bazel-skylib."""
 
 load("@bazel_skylib//lib:unittest.bzl", "register_unittest_toolchains")