Add script/bootstrap file.

README.md

@@ -101,8 +101,7 @@ We use `cabal's` [Nix-style local builds][nix] for development. To get started q
 ```bash
 git clone git@github.com:github/semantic.git
 cd semantic
-git submodule sync --recursive && git submodule update --init --recursive --force
-cabal new-update
+script/bootstrap
 cabal new-build
 cabal new-test
 cabal new-run semantic -- --help

script/bootstrap

@@ -0,0 +1,4 @@
+#!/bin/bash
+
+git submodule sync --recursive && git submodule update --init --recursive --force
+cabal new-update