First of all, you need to have a recent Linux distribution, Fedora 20/21, Ubuntu 14.04, ARCH Linux, SuSE Linux) and at least 15 GB of free space.

The heart of the OpenELEC project is our software build system. It supports a software building technique called cross-compiling; the process of creating executable code that runs on one hardware platform from something other than that platform. Cross compiling is a crucial function for the OpenELEC project for the following reasons:

Start by updating your system (on Ubuntu or other Debian-based distribution):

Note: Debian does not need "sudo" however the commands are identical once sudo is removed.

Note: at least gcc-4.7 is required.

sudo apt-get update sudo apt-get upgrade sudo apt-get install make

Reconfigure to bash so we have best possible script compatibility

sudo dpkg-reconfigure dash

and select no, to install bash as the default

Then, install build tools

you will need libxml-parser-perl

sudo apt-get install libxml-parser-perl

yum install autoconf automake binutils cpp cvs gcc gcc-c++ glibc-devel glibc-headers glibc-static kernel-devel kernel-headers libmpc libstdc++-devel libstdc++-static ncurses-devel perl-libintl perl-Test-Harness perl-Text-Unidecode perl-Thread-Queue texinfo

git clone https://github.com/OpenELEC/OpenELEC.tv.git

A new folder called OpenELEC.tv will be created.

Be sure to have lot of free space - at least 15 GB. Better more than less.

In a terminal go to the folder that was just created.
cd OpenELEC.tv

Take a break after hitting return.
When the build completes, you will find the fresh build in the target directory of your build directory OpenELEC.tv/target/

If you need to clean and start over do a make clean and then start the build process again.