This repo contains the tiny core extensions I've built and the scripts I wrote to make them (one extension as of this writing).
To build the extension, clone the repo to a Linux system (I used Tiny Core). Install mksquashfs and tcztools.
To download and build s3cmd, run:
$./s3cmd-get
$./s3cmd-build
This will set up your /tmp dir, and now if you want to build the extension, run:
$./tcz-pack s3cmd.tcz
I had to fix an issue in the tcz-pack in tcztools, which is why I included my own. You could not use tcz-pack, but then you have to do the list, md5, and mksquashfs stuff some other way.
Now, you should have a new tcz extension in /tmp/tcztools/.