A simple COFF/PE packer base on this tutorial and this blogpost for TLS, and this blogpost for exports.
Also, not perfect but this documentation.
It is pretty unusable and is just a POC to try out zig build scripts and to learn about the PE format.
Update the path to the binary to embed in build.zig and run:
zig build -Dtarget=x86_64-windows -Doptimize=ReleaseSmall