set up build environment for release executables, add checklist

Author: patrickfreed

.swift-version

@@ -38,6 +38,9 @@ let package = Package(
             dependencies: [
                 "SwiftlyCore",
                 "CLibArchive",
+            ],
+            linkerSettings: [
+                .linkedLibrary("z")
             ]
         ),
         .systemLibrary(

Package.swift

@@ -0,0 +1,21 @@
+# Releasing swiftly
+
+1. Check out the commit you wish to create a release for. Ensure no other local modifications or changes are present.
+
+1. Ensure the version string in `Swiftly.swift` is accurate. If it is not, push another commit updating it to the proper value.
+
+1. Create a tag on that commit with the format "x.y.z". Do not omit "z", even if its value is 0.
+
+1. Build the executables for the release (do this once on an x86_64 machine and once on an aarch64 one):
+
+    - In the root of the `swiftly` repository, run the following command: `docker build -t <image name> -f scripts/build.dockerfile .`
+    - Then, run `container_id=$(docker create <image name>)`
+    - Retrieve the built swiftly executable with `docker cp "$container_id:/swiftly" <executable name>`
+      - For ARM, the executable name should be `swiftly-aarch64-unknown-linux-gnu`
+      - For x86_64, the executable name should be `swiftly-x86_64-unknown-linux-gnu`
+    - Clean up the leftover container with `docker rm -v $container_id`
+    - Clean up the leftover image with `docker rm -f <image name>`
+
+1. Push the tag to `origin`.
+
+1. Go to the GitHub page for the new tag, click edit tag, add an appropriate description, attach the prebuilt executables, and click "Publish Release".

RELEASING.md

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+
+set -o errexit
+
+# TODO detect platform
+LIBARCHIVE_VERSION=3.6.1
+
+mkdir /tmp/archive-build
+pushd /tmp/archive-build
+curl --remote-name \
+     --location \
+     "https://github.com/libarchive/libarchive/releases/download/v$LIBARCHIVE_VERSION/libarchive-$LIBARCHIVE_VERSION.tar.gz"
+tar -xzf "libarchive-$LIBARCHIVE_VERSION.tar.gz"
+
+cd "libarchive-$LIBARCHIVE_VERSION"
+./configure \
+    --enable-shared=no \
+    --with-pic \
+    --without-nettle \
+    --without-openssl \
+    --without-lzo2 \
+    --without-expat \
+    --without-xml2 \
+    --without-bz2lib \
+    --without-libb2 \
+    --without-iconv \
+    --without-zstd \
+    --without-lzma \
+    --without-lz4 \
+    --disable-acl \
+    --disable-bsdtar \
+    --disable-bsdcat
+make
+make install
+popd

scripts/build-libarchive.sh

@@ -0,0 +1,25 @@
+# Dockerfile used to build a statically-linked swiftly executable for generic GNU/Linux platforms.
+# See RELEASING.md for information on how to use this file.
+
+FROM swiftlang/swift:nightly-amazonlinux2
+
+# swiftly build depdenencies
+RUN yum install -y \
+    curl \
+    gcc \
+    make
+
+COPY . /tmp/swiftly
+WORKDIR /tmp/swiftly
+
+RUN ./scripts/build-libarchive.sh
+
+RUN swift build \
+      --static-swift-stdlib \
+      --configuration release
+
+RUN mv .build/release/swiftly /swiftly
+RUN strip /swiftly
+
+RUN /swiftly --version
+RUN ldd /swiftly