Build protoc in Travis

This mostly fixes the Travis-CI build.

Author: ejona86

.buildscript/build-proto.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+
+set -ev
+
+PROTO_VERSION="$1"
+PROTO_FOLDER="/tmp/proto$PROTO_VERSION"
+
+# Can't check for presence of directory as cache auto-creates it.
+if [ ! -f "$PROTO_FOLDER/bin/protoc" ]; then
+  wget -O - "https://github.com/google/protobuf/archive/v${PROTO_VERSION}.tar.gz" | tar xz -C /tmp
+  cd "/tmp/protobuf-${PROTO_VERSION}"
+  ./autogen.sh
+  ./configure --prefix="$PROTO_FOLDER" --disable-shared
+  make -j2
+  make install
+fi
+echo "protoc is available at $PROTO_FOLDER/bin/protoc"

.travis.yml

@@ -1,6 +1,24 @@
+sudo: false
+
 language: java
+
+notifications:
+  email: false
+
+env:
+  global:
+    - PROTO_VERSION=2.4.1
+    - PATH="/tmp/proto$PROTO_VERSION/bin:$PATH"
+
 jdk:
   - oraclejdk8
   - oraclejdk7
   - openjdk7
   - openjdk6
+
+before_install:
+  - .buildscript/build-proto.sh $PROTO_VERSION
+
+cache:
+  directories:
+    - /tmp/proto$PROTO_VERSION