Create initial Dockerfile and README.md

This seems to work fine locally.

Dockerfile

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+# Use Debian 8.0 "Jessie" as the base for our Rust musl toolchain.
+FROM debian:jessie
+
+# Make sure we have basic dev tools for building C libraries, and any
+# shared library dev packages we'll need, and create a `rust` user in
+# whose home directory we'll install the Rust compilers.
+#
+# Our goal here is to support the musl-libc builds and Cargo builds needed
+# for a large selection of the most popular crates.
+#
+# We also set up a `rust` user by default, in whose account we'll install
+# the Rust toolchain.  This user has sudo privileges if you need to install
+# any more software.
+RUN apt-get update && \
+    apt-get install -y build-essential sudo git curl file xutils-dev cmake && \
+    apt-get clean && rm -rf /var/lib/apt/lists/* && \
+    useradd rust --user-group --create-home --shell /bin/bash --groups sudo && \
+    echo "%sudo   ALL=(ALL:ALL) NOPASSWD:ALL" >> /etc/sudoers
+
+# Set up our path with all the binary directories we're going to create,
+# including those for the musl-gcc toolchain and for our Rust toolchain.
+ENV PATH=/home/rust/.cargo/bin:/usr/local/musl/bin:/usr/local/bin:/usr/bin:/bin
+
+# Build the musl-libc toolchain, which installs itself in /usr/local/musl.
+WORKDIR /musl
+RUN git clone git://git.musl-libc.org/musl && cd musl && \
+    ./configure && make install
+
+# Build a static library version of OpenSSL using musl-libc.  This is
+# needed by the popular Rust `hyper` crate.
+RUN VERS=1.0.2g && \
+    curl -O https://www.openssl.org/source/openssl-$VERS.tar.gz && \
+    tar xvzf openssl-$VERS.tar.gz && cd openssl-$VERS && \
+    env CC=musl-gcc ./config --prefix=/usr/local/musl && \
+    make depend && make && make install
+ENV OPENSSL_INCLUDE_DIR=/usr/local/musl/include/ \
+    OPENSSL_LIB_DIR=/usr/local/musl/lib/ \
+    OPENSSL_STATIC=1
+
+# (Please feel free to submit pull requests for musl-libc builds of other C
+# libraries needed by the most popular and common Rust crates, to avoid
+# everybody needing to build them manually.)
+
+# Delete our musl-libc build directory.
+RUN rm -rf /musl
+
+# Mount the source code we want to build on /home/rust/src.  We do this as
+# user `rust`, which will be uid 1000, gid 1000 outside the container.
+VOLUME ["/home/rust/src"]
+USER rust
+WORKDIR /home/rust/src
+
+# Install our Rust toolchain and the `musl` target.  We patch the
+# command-line we pass to the installer so that it won't attempt to
+# interact with the user or fool around with TTYs.  We also set the default
+# `--target` to musl so that our users don't need to keep overriding it
+# manually.
+RUN curl https://sh.rustup.rs -sSf | sed 's,run "$_file" < /dev/tty,run "$_file" -y,' | sh && \
+    rustup default stable && \
+    rustup target add x86_64-unknown-linux-musl && \
+    echo "[build]\ntarget = \"x86_64-unknown-linux-musl\"\n" >> /home/rust/.cargo/config

Dockerfile.example

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+# -*- mode: dockerfile -*-
+#
+# An example Dockerfile showing how to add new static C libraries using
+# musl-gcc.
+
+FROM ekidd/rust-musl-builder:latest
+
+# Build a static copy of zlib.
+RUN VERS=1.2.8 && \
+    mkdir -p /home/rust/libs && cd /home/rust/libs && \
+    curl -LO http://zlib.net/zlib-$VERS.tar.gz && \
+    tar xzf zlib-$VERS.tar.gz && cd zlib-$VERS && \
+    CC=musl-gcc ./configure --static --prefix=/usr/local/musl && \
+    make && sudo make install && \
+    rm -rf /home/rust/libs/zlib-$VERS.tar.gz /home/rust/libs/zlib-$VERS

README.md

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+# `rust-musl-builder`: Docker container for easily building static Rust binaries
+
+Do you want to compile a completely static Rust binary with no external
+dependencies?  If so, try:
+
+```sh
+alias rust-musl-builder='docker run --rm -it -v "$(pwd)":/home/rust/src ekidd/rust-musl-builder'
+rust-musl-builder cargo build --rebase
+```
+
+This command assumes that `$(pwd)` is readable and writable by uid 1000,
+gid 1000.  It will output binaries in
+`target/x86_64-unknown-linux-musl/release`.  At the moment, it doesn't
+attempt to cache libraries between builds, so this is best reserved for
+making final release builds.
+
+## Deploying your Rust application
+
+With a bit of luck, you should be able to just copy your application binary
+from `target/x86_64-unknown-linux-musl/release`, and install it directly on
+any reasonably modern x86_64 Linux machine.  In particular, you should be
+able to copy your Rust application into an
+[Alpine Linux container][].
+
+## How it works
+
+`rust-musl-builder` uses [musl-libc][], [musl-gcc][], and the new
+[rustup][] `target` support.  It includes static versions of several
+libraries:
+
+- The standard `musl-libc` libraries.
+- OpenSSL, which is needed by many Rust applications.
+
+## Adding more C libraries
+
+If you're using Docker crates which require specific C libraries to be
+installed, you can create a Dockerfile based on this one, and use
+`musl-gcc` to compile the libraries you need.  For example:
+
+```Dockerfile
+FROM ekidd/rust-musl-builder:latest
+
+RUN VERS=1.2.8 && \
+    mkdir -p /home/rust/libs && cd /home/rust/libs && \
+    curl -LO http://zlib.net/zlib-$VERS.tar.gz && \
+    tar xzf zlib-$VERS.tar.gz && cd zlib-$VERS && \
+    CC=musl-gcc ./configure --static --prefix=/usr/local/musl && \
+    make && sudo make install && \
+    rm -rf /home/rust/libs/zlib-$VERS.tar.gz /home/rust/libs/zlib-$VERS
+```
+
+This usually involves a bit of experimentation for each new library, but it
+seems to work well for most simple, standalone libraries.
+
+If you need an especially common library, please feel free to submit a pull
+request adding it to the main `Dockerfile`!  We'd like to support popular
+Rust crates out of the box.
+
+[Alpine Linux container]: https://hub.docker.com/_/alpine/
+[musl-libc]: http://www.musl-libc.org/
+[musl-gcc]: http://www.musl-libc.org/how.html
+[rustup]: https://www.rustup.rs/