Vendor the external cookbooks

Knife-Zero doesn't include Berkshelf support, so vendoring everything in
the repo is convenient again

cookbooks/build-essential/resources/xcode_command_line_tools.rb

@@ -0,0 +1,57 @@
+#
+# Cookbook:: build-essential
+# Resource:: xcode_command_line_tools
+#
+# Copyright:: 2014-2018, Chef Software, Inc.
+#
+# 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.
+#
+
+resource_name :xcode_command_line_tools
+
+action :install do
+  if installed?
+    Chef::Log.debug("#{new_resource} already installed - skipping")
+  else
+    converge_by("Install #{new_resource}") do
+      # This script was graciously borrowed and modified from Tim Sutton's
+      # osx-vm-templates at https://github.com/timsutton/osx-vm-templates/blob/b001475df54a9808d3d56d06e71b8fa3001fff42/scripts/xcode-cli-tools.sh
+      execute 'install XCode Command Line tools' do
+        command <<-EOH.gsub(/^ {14}/, '')
+          # create the placeholder file that's checked by CLI updates' .dist code
+          # in Apple's SUS catalog
+          touch /tmp/.com.apple.dt.CommandLineTools.installondemand.in-progress
+          # find the CLI Tools update
+          PROD=$(softwareupdate -l | grep "\*.*Command Line" | tail -n 1 | awk -F"*" '{print $2}' | sed -e 's/^ *//' | tr -d '\n')
+          # install it
+          softwareupdate -i "$PROD" --verbose
+          # Remove the placeholder to prevent perpetual appearance in the update utility
+          rm -f /tmp/.com.apple.dt.CommandLineTools.installondemand.in-progress
+        EOH
+      end
+    end
+  end
+end
+
+action_class do
+  #
+  # Determine if the XCode Command Line Tools are installed
+  #
+  # @return [true, false]
+  #
+  def installed?
+    cmd = Mixlib::ShellOut.new('pkgutil --pkgs=com.apple.pkg.CLTools_Executables')
+    cmd.run_command
+    cmd.error? ? false : true
+  end
+end