Over time, we've accumulated a few different tools for building Ext. Each has advantages and disadvantages, but no one has ever fully explained what the options are and why you might choose to do one or the other. The other main issue is that the tools are not documented very well, so many people have trouble figuring out how to use them.
I wrote this tutorial to address all of those issues. It covers how to build Ext using:
Windows-only JS Builder (both the GUI and console versions are covered)
The tutorial also provides examples of automated building via shell scripts (Mac/Unix) and batch files (Win). If you are an SVN subscriber and have been trying to figure out how to build the latest dev code, or if you are deploying your code to production and trying to figure out the best way to manage your JS files, this is the tutorial for you.