1. Install build dependencies

Python 2.7.X
Autoconf 2.13
Yasm 1.2.0 or newer
Perl
Gnu C Compiler version 4.9.3 or newer (9.X.X reccomended)

2. Install runtime dependencies

* Note that to make your life easier, check DEPEND.yourdistrobution for 
commands you can copypaste into your terminal instead of looking of 
looking up package names by hand

libXt
zip
freetype
fontconfig
glibc
libffi
dbus
dbus-glib
gtk+2
alsa-lib
jack2
libvpx (1.7.X reccomended. 1.8.X is untested)
ffmpeg

3. clone and checkout code repositories

clone the Universal XUL Platform codebase somewhere

$ git clone https://github.com/MoonchildProductions/UXP.git

checkout the supported Web Browser supported PM_RELEASE snapshot.
You can check what is the latest supported release by looking at
webbrowser/config/version.txt . In this example we will use 2.8.1

$ cd UXP
$ git checkout PM28.8.2_Release

clone the web browser application repo into the 'application' folder

$ cd application
$ git clone https://git.nuegia.net/webbrowser.git

copy the example Mach build system config into the root of UXP

$ cp webbrowser/doc/mozconfig.example ../.mozconfig

Optionally adjust .mozconfig to better fit your needs
then go to the root of UXP

$ cd ..

4. compile, test, and package Web Browser

./mach build

if this completes successfully you can test your build before packaging it

./mach run

if all is well package it

./mach package

and then install the resulting distrobution tarball on your system.