Add CIPD binary installation to DEPS runhooks.

bootstrap/cipd/doc/infra/tools/protoc/linux-amd64/README.md

+# `infra/tools/protoc/linux-amd64`
+## Building Instructions.
+
+Choose a build directory. We'll use the enviornment variable `$ROOT` to
+represent it.
+
+    $ cd $ROOT
+
+Clone the `protobuf` repository:
+
+    $ git clone https://github.com/google/protobuf
+
+Run the build. We include the following additional configuration flags:
+- `--disable-shared`: Build a static library.
+- `--prefix $ROOT/PREFIX`: The installation prefix. This allows us to install
+                           locally, so we don't need root.
+
+Build:
+
+    $ cd protobuf
+    $ ./autogen.sh
+    $ ./configure --disable-shared --prefix $ROOT/PREFIX
+    $ make -j24 install
+
+This will install the generator to `$ROOT/PREFIX/bin/protoc`. Afterwards, strip
+the binary. This removes symbols and debugging information, including your
+username, from the binary, reducing its size from ~40MiB to ~3MiB.
+
+    $ strip -g $ROOT/PREFIX/bin/protoc
+
+Create package and deploy to `cipd` server.
+
+    $ cipd create \

[Vadim Sh., 2015/09/24 19:28:30]

nit: slap a git_commit:... tag too with SHA1 of protobuf.git, just to keep track
of what's what.

Something like:
cipd create \
  -name "infra/tools/protoc/linux-amd64" \
  -in $ROOT/PREFIX/bin \
  -tag "git_commit:`git rev-parse HEAD`"

[dnj, 2015/09/24 20:29:56]

Done.

+      -name "infra/tools/protoc/linux-amd64" \
+      -in $ROOT/PREFIX/bin