it loops through the named folders (builddir1, builddir2 and builddir3 in my example), builds the source in that folders and copies the resulting rockbox.zip to the current folder and prefixes the files with the foldername. So you just need to adjust your folder names apropriately and are done.
Of course you can extend that to be a bit more flexible about the names of the resulting files. You could omit the rockbox.zip ending and simply use the folder name (so builddir1 will create a builddir1.zip) or add a prefix (and make builddir1 create rockbox-builddir1.zip)
It's quite straightforward bash without anything special. FYI, I'm building the whole set of manuals frequently in a similar way.