.github, config: cross-compile an arm64 asset

And install Zig via script, rather than snap. One benefit is that it
allows us to pin a Zig version.

The script is adapted from one I added to the Exercism Zig repo [1].

[1] exercism/zig@9dfb95f031b1

.github/bin/cross-compile

@@ -0,0 +1,18 @@
+#!/usr/bin/env sh
+
+nimble --accept install --depsOnly
+
+artifacts_dir='artifacts'
+mkdir -p "${artifacts_dir}"
+
+target='aarch64-linux-musl'
+arch='arm64'
+os='linux'
+nimble --verbose build --cpu:"${arch}" --os:"${os}" -d:release -d:zig -d:target:"${target}"
+
+binary_name='configlet'
+build_tag="${GITHUB_REF_NAME}"
+artifact_file="${artifacts_dir}/${binary_name}_${build_tag}_${os}_${arch}.tar.gz"
+tar -cvzf "${artifact_file}" "${binary_name}"
+
+gh release upload "${build_tag}" "${artifacts_dir}/${artifact_file}"

.github/bin/linux-install-musl

@@ -0,0 +1,2 @@
+#!/usr/bin/env sh
+sudo apt-get install musl-dev musl-tools

.github/bin/linux-install-zig

@@ -0,0 +1,45 @@
+#!/usr/bin/env bash
+set -eo pipefail
+
+version='0.11.0' # 2023-08-04
+release_name="zig-linux-x86_64-${version}"
+archive="${release_name}.tar.xz"
+url="https://ziglang.org/download/${version}/${archive}"
+
+curlopts=(
+  --silent
+  --show-error
+  --fail
+  --location
+  --retry 3
+)
+
+# Download the release archive.
+echo "Downloading Zig release archive..." >&2
+curl "${curlopts[@]}" --output "${archive}" "${url}"
+
+# Check that the archive has the expected hash.
+echo "Verifying archive..." >&2
+archive_sha256='2d00e789fec4f71790a6e7bf83ff91d564943c5ee843c5fd966efc474b423047'
+echo "${archive_sha256} ${archive}" | sha256sum -c -
+
+# Extract the archive, then remove it.
+echo "Extracting archive..." >&2
+tar xJf "${archive}"
+rm "${archive}"
+
+# Add zig directory to `GITHUB_PATH`.
+zig_dir="$(pwd)/${release_name}"
+echo "${zig_dir}" >> "${GITHUB_PATH}"
+
+# Install `zigcc`, which is just a wrapper for `zig cc`. We need this because
+# the value of e.g. `--clang.exe` cannot contain a space (Nim requires the value
+# to be an executable, not a command).
+zigcc_path="${zig_dir}/zigcc"
+printf '#!/usr/bin/env sh\nzig cc $@\n' > "${zigcc_path}"
+chmod +x "${zigcc_path}"
+
+# Print the versions of Zig and Clang.
+"${zig_dir}"/zig version
+"${zig_dir}"/zig cc --version
+echo "Successfully installed Zig ${version}."

.github/workflows/build.yml

@@ -34,9 +34,9 @@ jobs:
         with:
           fetch-depth: 0 # Allows using `git log` to set initial release notes.
 
-      - name: On Linux, install Zig
+      - name: On Linux, install musl
         if: matrix.os == 'linux'
-        run: ./.github/bin/linux-install-build-tools
+        run: ./.github/bin/linux-install-musl
 
       - name: Install Nim
         uses: iffy/install-nim@ac410af52523f06e0fa037ee81d06ead7b95692c
@@ -62,9 +62,34 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
-  checksums:
+  cross-compile:
     needs: [build]
     runs-on: ubuntu-22.04
+    name: cross-compile
+    permissions:
+      contents: write
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9
+
+      - name: Install Nim
+        uses: iffy/install-nim@ac410af52523f06e0fa037ee81d06ead7b95692c
+        with:
+          version: "binary:2.0.0"
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Install Zig
+        run: ./.github/bin/linux-install-zig
+
+      - name: Cross-compile
+        run: ./.github/bin/cross-compile
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+  checksums:
+    needs: [cross-compile]
+    runs-on: ubuntu-22.04
     name: Upload signatures and checksums
     permissions:
       contents: write

.github/workflows/tests.yml

@@ -37,9 +37,9 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9
 
-      - name: On Linux, install Zig
+      - name: On Linux, install musl
         if: matrix.os == 'linux'
-        run: ./.github/bin/linux-install-build-tools
+        run: ./.github/bin/linux-install-musl
 
       - name: Install Nim
         uses: iffy/install-nim@ac410af52523f06e0fa037ee81d06ead7b95692c

config.nims

@@ -12,6 +12,16 @@ switch("mm", "refc")
 patchFile("stdlib", "json", "src/patched_stdlib/json")
 patchFile("stdlib", "parsejson", "src/patched_stdlib/parsejson")
 
+if defined(zig) and findExe("zigcc").len > 0:
+  switch("cc", "clang")
+  # We can't write `zig cc` below, because the value cannot contain a space.
+  switch("clang.exe", "zigcc")
+  switch("clang.linkerexe", "zigcc")
+  const target {.strdefine.} = ""
+  if target.len > 0:
+    switch("passC", "-target " & target)
+    switch("passL", "-target " & target)
+
 if defined(release):
   switch("opt", "size")
   switch("passC", "-flto")
@@ -21,15 +31,8 @@ if defined(release):
     switch("passL", "-s")
     switch("passL", "-static")
 
-  if defined(linux):
-    if findExe("zigcc").len > 0 and defined(amd64):
-      switch("cc", "clang")
-      # We can't write `zig cc` below, because the value cannot contain a space.
-      switch("clang.exe", "zigcc")
-      switch("clang.linkerexe", "zigcc")
-      switch("passC", "-target x86_64-linux-musl")
-      switch("passL", "-target x86_64-linux-musl")
-    elif defined(gcc):
+  if defined(linux) and not defined(zig):
+    if defined(gcc):
       switch("gcc.exe", "musl-gcc")
       switch("gcc.linkerexe", "musl-gcc")
     elif defined(clang):