Introduce polkadot-musl-builder

polkadot-musl-builder/README.md

@@ -0,0 +1,63 @@
+# Introduction
+
+[polkadot-musl-builder](./polkadot-musl-builder.sh) is script which builds a
+statically-linked Polkadot using musl.
+
+Note: This script is not self-contained! It's assumed that it will be ran in a
+clean slate container where we'll be free to mess around with the system's
+files and potentially leave the system's state broken in case of failures. You
+should not use it directly in your system.
+
+# Usage
+
+## 1. Create the Dockerfile
+
+Create a Dockerfile (the base image should be Debian-based) which will run the
+script. For demonstration's sake we'll use `rust:1.56.0-slim-bullseye`, which
+uses Rust 1.56, which is is the latest one right now, but it's recommended that
+you pick an image which matches Polkadot's Rust version by the time you're
+running this script.
+
+```bash
+echo "
+FROM rust:1.56.0-slim-bullseye
+
+COPY ./polkadot-musl-builder.sh /polkadot-musl-builder.sh
+RUN chmod +x /polkadot-musl-builder.sh
+
+# Override the default definitions through ENV directives if you'd like
+# Check the polkadot-musl-builder.sh source code for all the available definitions
+# POLKADOT_BRANCH can also be a tag instead of a branch name
+ENV POLKADOT_BRANCH=master
+
+# Run the script to generate the Polkadot binary
+RUN /polkadot-musl-builder.sh build
+" > Dockerfile
+```
+
+TODO: `/polkadot-musl-builder.sh build` runs all the build steps in a single
+`RUN` directive and therefore doesn't leverage caching between it's multiple
+internal steps; it should be possible to separate each step in a different
+`RUN` directive to overcome this.
+
+## 2. Build the binary inside a container
+
+```sh
+docker build . -t polkadot:musl
+```
+
+The resulting image will have the statically-linked Polkadot binary placed at
+`/polkadot`. This binary can be extracted by creating a temporary container and
+using `docker container cp`, as demonstrated below:
+
+```bash
+docker container create --name tmp polkadot:musl
+docker container cp tmp:/polkadot .
+docker container rm tmp
+```
+
+## 3. Check the binary
+
+`ldd ./polkadot` should display "statically linked".
+
+You can simply run it with `./polkadot`.