Clean up the Makefile and the build scripts

Summary: As Aaron suggested, there are quite some problems with our Makefile and scripts. So in this diff I did some cleanup for them and revise some part of the scripts/makefile to help people better understand some mysterious parts.

Test Plan:
Ran make in several modes;
Ran the updated scripts.

Reviewers: dhruba, emayanke, akushner

Differential Revision: https://reviews.facebook.net/D12285

build_tools/build_java.sh

@@ -0,0 +1,86 @@
+#!/bin/bash -e
+function print_usage {
+  echo "Usage: $0 [build | release | bump_version version ]"
+}
+
+function check_env {
+  if [ -z $LEVELDB_HOME ] ; then
+    echo "Expect LEVELDB_HOME to be SET"
+    exit 1
+  fi
+  if [ -z $JAVA_HOME ] ; then
+    export JAVA_HOME=/usr/local/jdk-6u14-64/
+    echo "JAVA_HOME not set. Assuming JAVA_HOME=$JAVA_HOME"
+  fi
+  if [ -z $LEVELDBJNI_HOME ] ; then
+    export LEVELDBJNI_HOME=$LEVELDB_HOME/java/leveldbjni/
+    echo "LEVELDBJNI_HOME not set. Assuming LEVELDBJNI_HOME=$LEVELDBJNI_HOME"
+  fi
+  if [ -z $SNAPPY_HOME ] ; then
+    export SNAPPY_HOME="/home/dhruba/snappy-1.0.5"
+    echo "SNAPPY_HOME not set. Assuming SNAPPY_HOME=$SNAPPY_HOME"
+  fi
+  if [ -z $LEVELDB_PATCH ] ; then 
+    LEVELDB_PATCH=$LEVELDB_HOME/java/leveldbjni/db.h.patch
+    echo "LEVELDB_PATCH not set. Assuming LEVELDB_PATCH=$LEVELDB_PATCH"
+  fi
+}
+
+function build {
+  cd $LEVELDB_HOME
+  git apply $LEVELDB_PATCH
+  make clean libleveldb.a
+  cd $LEVELDB_HOME/java/leveldb/leveldb-api
+  mvn clean package
+  cd $LEVELDBJNI_HOME
+  mvn clean install -P linux64
+  cd $LEVELDB_HOME
+  git checkout $LEVELDB_HOME/include/leveldb/db.h
+}
+
+function release {
+  cd $LEVELDB_HOME
+  git apply $LEVELDB_PATCH
+  make clean libleveldb.a
+  cd $LEVELDB_HOME/java/leveldb/leveldb-api
+  mvn clean package
+  cd $LEVELDBJNI_HOME
+  mvn deploy -P linux64 -DskipTests
+  cd $LEVELDB_HOME
+  git checkout $LEVELDB_HOME/include/leveldb/db.h
+}
+
+CMD=$1
+if [ -z $CMD ]; then
+  print_usage
+  exit 1
+fi
+
+case "$CMD" in 
+  build) 
+    check_env
+    build
+    ;;
+  bump_version)
+    if [ -z $2 ] ; then
+      echo "bump_version requires a version.no parameter at the end"
+      exit 1
+    fi 
+    check_env
+    VERSION=$2
+    pushd $LEVELDBJNI_HOME
+    mvn versions:set -DnewVersion="$VERSION"
+    popd
+    echo "VERSION SET TO $VERSION"
+    ;;
+  release)
+    check_env
+    pushd $LEVELDBJNI_HOME
+    release
+    popd
+    ;;
+  *)
+    print_usage
+    exit 1
+    ;;
+esac