cross compile lib sodium to manually place it before doing npm install

cross_compile_sodium.sh

#!/bin/bash

# This assumes that you have android ndk installed at ~/android-ndk-r11c

apt-get install build-essential libssl-dev libtool -y

# check out libsodium
git clone https://github.com/	jedisct1/libsodium.git

export TOOLCHAIN=$PWD/android-toolchain
mkdir -p $TOOLCHAIN
~/android-ndk-r11c/build/tools/make-standalone-toolchain.sh \
    --toolchain=arm-linux-androideabi-4.9 \
    --arch=arm \
    --install-dir=$TOOLCHAIN \
    --platform=android-21
export PATH=$TOOLCHAIN/bin:$PATH
export AR=$TOOLCHAIN/bin/arm-linux-androideabi-ar
export CC=$TOOLCHAIN/bin/arm-linux-androideabi-gcc
export CXX=$TOOLCHAIN/bin/arm-linux-androideabi-g++
export LINK=$TOOLCHAIN/bin/arm-linux-androideabi-g++