ci: add early arm64 builds and SwiftLint checks (#2)

scripts/lint.sh

@@ -0,0 +1,38 @@
+#!/bin/bash
+set -euo pipefail
+
+tools_root="${1:?Usage: scripts/lint.sh /absolute/path/to/tools-directory}"
+case "$tools_root" in
+    /*) ;;
+    *) echo "The tools directory must be an absolute path." >&2; exit 2 ;;
+esac
+
+repo_root="$(cd "$(dirname "$0")/.." && pwd)"
+version="0.65.1"
+checksum="c1e429b0599cf1b516f369a2d9ec04eaf0e436f3c12b637df8851fa52ff694d0"
+install_root="$tools_root/swiftlint-$version"
+binary="$install_root/swiftlint"
+
+if [[ ! -x "$binary" ]]; then
+    mkdir -p "$tools_root"
+    download_root="$(mktemp -d "$tools_root/swiftlint-download.XXXXXX")"
+    trap 'rm -rf "$download_root"' EXIT
+    curl --fail --location --silent --show-error --retry 3 \
+        --proto '=https' --proto-redir '=https' \
+        "https://github.com/realm/SwiftLint/releases/download/$version/portable_swiftlint.zip" \
+        --output "$download_root/portable_swiftlint.zip"
+    printf '%s  %s\n' "$checksum" "$download_root/portable_swiftlint.zip" | shasum -a 256 -c -
+    mkdir "$download_root/extracted"
+    unzip -q "$download_root/portable_swiftlint.zip" -d "$download_root/extracted"
+    mkdir -p "$install_root"
+    cp "$download_root/extracted/swiftlint" "$binary"
+    chmod +x "$binary"
+fi
+
+if [[ "$("$binary" version)" != "$version" ]]; then
+    echo "Expected SwiftLint $version. Remove $install_root and retry." >&2
+    exit 1
+fi
+
+cd "$repo_root"
+"$binary" lint --strict --no-cache --config .swiftlint.yml