tools: add links for add-det and linkdupes

<a href="https://packages.debian.org/sid/strip-nondeterminism" class="btn btn-outline-primary btn-sm">Debian package</a>

<a href="https://archlinux.org/packages/extra/any/strip-nondeterminism" class="btn btn-outline-primary btn-sm">Arch Linux package</a>

#### add-determinism

The binary is actually called `add-det`.

A tool similar to `strip-nondeterminism` that does post-processing to

remove some common irreproducibilities in package builds.

Used for post-build cleanup in rpm package builds.

It is written in Rust and implements

cleaning of archive formats (static archives, zip files, jar files, gzip files),

and rewriting of Python bytecode pyc files.

<a href="https://github.com/keszybz/add-determinism" class="btn btn-outline-primary btn-sm">Git</a>

<a href="https://github.com/keszybz/add-determinism/issues" class="btn btn-outline-primary btn-sm">Issues</a>

<a href="https://src.fedoraproject.org/rpms/rust-add-determinism" class="btn btn-outline-primary btn-sm">Fedora Linux package</a>

<a href="https://archlinux.org/packages/extra/x86_64/add-determinism/" class="btn btn-outline-primary btn-sm">Arch Linux package</a>

<a href="https://github.com/NixOS/nixpkgs/blob/nixos-unstable/pkgs/by-name/ad/add-determinism/package.nix" class="btn btn-outline-primary btn-sm">NixOS package</a>

<a href="https://formulae.brew.sh/formula/add-determinism" class="btn btn-outline-primary btn-sm">Brew formula</a>

#### linkdupes

Yet another program to hardlink files,

but intended for package builds.

It takes `$SOURCE_DATE_EPOCH` into account to smartly clamp mtimes.

Also takes SELinux context into account.

(Files which will have *different* SELinux context when deployed must not be hardlinked.)

It is developed together with `add-determinism`.

See links above.

#### disorderfs

Problems with [unstable order of inputs](/docs/stable-inputs/) or other