Limit concurrent NativeAOT compiles to stop MSBuild nodes dying of memory pressure [CI]

ci/with-aot-slot.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+# 同一时间最多 N 个 NativeAOT 编译（ILCompiler 加链接每个要占几 GB 内存）。dev-image 里后端和三个 RID 的 Agent 同时开编译时，
+# 内存不够，系统杀掉 MSBuild 的工作进程（MSB4166 Child node exited prematurely），整条流水线失败。
+# 用法：with-aot-slot.sh <命令...>   环境：MOSHIRO_AOT_SLOTS（默认 2）、MOSHIRO_AOT_SLOT_DIR、MOSHIRO_AOT_SLOT_WAIT（等空位的秒数，默认 3000）
+# flock --close：命令自己拿不到锁的文件描述符，锁只由 flock 进程持有，所以命令遗留的后台进程（比如 MSBuild 复用的节点）不会让空位一直占着。
+set -euo pipefail
+[[ $# -gt 0 ]] || { echo "usage: with-aot-slot.sh <command> [args...]" >&2; exit 2; }
+slots="${MOSHIRO_AOT_SLOTS:-2}"
+dir="${MOSHIRO_AOT_SLOT_DIR:-/home/justme/woodpecker/cache/aot-slots}"
+wait_seconds="${MOSHIRO_AOT_SLOT_WAIT:-3000}"
+mkdir -p "$dir"
+deadline=$((SECONDS + wait_seconds))
+announced=false
+while :; do
+  for ((slot = 0; slot < slots; slot++)); do
+    status=0
+    flock --close --nonblock --conflict-exit-code 200 "$dir/slot-$slot" "$@" || status=$?
+    # 200 = 这个空位被占着，换下一个；其他返回码是命令自己的结果
+    [[ "$status" != 200 ]] && exit "$status"
+  done
+  if ((SECONDS >= deadline)); then
+    echo "no NativeAOT slot became free within ${wait_seconds}s" >&2
+    exit 1
+  fi
+  [[ "$announced" == true ]] || { echo "waiting for a free NativeAOT slot ($slots in use at most)" >&2; announced=true; }
+  sleep 3
+done