test: add reproducible Windows VM bundle harness

scripts/build

@@ -0,0 +1,22 @@
+#!/bin/sh
+# Host-safe entry point for the pinned RVBox build toolchain.
+set -eu
+
+repo_root=$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)
+target=${1:-build}
+shift || true
+
+case $target in
+    build|verify) ;;
+    *)
+        printf '%s\n' 'usage: scripts/build [build|verify]' >&2
+        exit 2
+        ;;
+esac
+[ "$#" -eq 0 ] || {
+    printf '%s\n' 'scripts/build does not accept additional arguments' >&2
+    exit 2
+}
+
+cd "$repo_root"
+exec docker compose -f deploy/compose.yaml run --rm toolchain make "$target"