build: run tests natively on ARM, Mac, and Windows in CI (#111)

scripts/ci/setup-system.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+set -eo pipefail
+
+function setup_linux () {
+    sudo apt-get update
+    sudo apt-get install -y --no-install-recommends make
+}
+
+function setup_mac () {
+    # Python and TCL both come pre-installed on Circle's mac executors, and both depend on wget in some way.
+    # Homebrew will auto-upgrade both of them when wget is installed/upgraded, triggering a chain of upgrades.
+    # Uninstall them both before adding wget to avoid burning time in CI for things we don't need.
+    brew remove --force python@3.9 tcl-tk
+    HOMEBREW_NO_AUTO_UPDATE=1 brew install wget
+}
+
+function setup_windows () {
+    choco install make mingw wget
+}
+
+function main () {
+    case $(uname) in
+        Linux)
+            setup_linux
+            ;;
+        Darwin)
+            setup_mac
+            ;;
+        MSYS_NT*)
+            setup_windows
+            ;;
+        *)
+            >&2 echo Error: unknown OS $(uname)
+            exit 1
+            ;;
+    esac
+}
+
+main ${@}