[llgo] add buildbot-slave config

[axw]

Summary

This patch adds the configuration used to deploy
the llgo-builder buildbot slave. The builder is
deployed to Google Compute Engine using Juju.

[pcc]

LGTM

I am unfamiliar with Juju, but assuming this does what it appears to do, this looks reasonable to me.

buildslave-config.yaml

+# This file contains llgo's configuration for the buildbot-slave Juju charm.
+# 
+# The slave is deployed with the following command in a Juju environment:
+#     juju deploy cs:~axwalk/buildbot-slave --config buildslave-config.yaml
+#
+# The charm generates a random password on first run, in the file
+# /srv/buildbot/password. If the password is regenerated, it must
+# be updated in the buildbot master.
+#
+buildbot-slave:
+  name: llgo-builder
+  master: lab.llvm.org:9990
+  admin-info: Andrew Wilkins <[e-mail]>
+  apt-packages: subversion git cmake gcc g++ gccgo python-dev
+  pip-versions: sqlalchemy==0.7.9 buildbot==0.8.5 buildbot_slave==0.8.5 twisted==12.0.0
+  post-install: |
+      #!/bin/bash
+      #
+      # Fetch, build and install Ninja.
+      rm -fr /tmp/ninja
+      cd /tmp && git clone git://github.com/martine/ninja.git
+      cd /tmp/ninja && ./configure.py --bootstrap
+      cp /tmp/ninja/ninja /usr/local/bin
+      # Fetch and unpack Go.
+      cd /tmp && wget https://storage.googleapis.com/golang/go1.4.2.linux-amd64.tar.gz
+      sha1sum <<EOF
+      5020af94b52b65cc9b6f11d50a67e4bae07b0aff go1.4.2.linux-amd64.tar.gz
+      EOF
+      cd /usr/local && tar xzf /tmp/go1.4.2.linux-amd64.tar.gz
+      ln -f -s /usr/local/go/bin/go /usr/local/bin/go
+