[tool] fixed scons --target=xmake

[Guozhanxin]

拉取/合并请求描述：(PR description)

[
之前修改结构的pr，破坏了xmake生成的功能。还原代码，修复功能
已经基于星火1号测试过了

为什么提交这份PR (why to submit this PR)

你的解决方案是什么 (what is your solution)

请提供验证的bsp和config (provide the config and bsp)

• BSP:

• .config:

• action:

]

当前拉取/合并请求的状态 Intent for your PR

必须选择一项 Choose one (Mandatory):

• 本拉取/合并请求是一个草稿版本 This PR is for a code-review and is intended to get feedback
• 本拉取/合并请求是一个成熟版本 This PR is mature, and ready to be integrated into the repo

代码质量 Code Quality：

我在这个拉取/合并请求中已经考虑了 As part of this pull request, I've considered the following:

• 已经仔细查看过代码改动的对比 Already check the difference between PR and old code
• 代码风格正确，包括缩进空格，命名及其他风格 Style guide is adhered to, including spacing, naming and other styles
• 没有垃圾代码，代码尽量精简，不包含#if 0代码，不包含已经被注释了的代码 All redundant code is removed and cleaned up
• 所有变更均有原因及合理的，并且不会影响到其他软件组件代码或BSP All modifications are justified and not affect other components or BSP
• 对难懂代码均提供对应的注释 I've commented appropriately where code is tricky
• 代码是高质量的 Code in this PR is of high quality
• 已经使用formatting 等源码格式化工具确保格式符合RT-Thread代码规范 This PR complies with RT-Thread code specification
• 如果是新增bsp, 已经添加ci检查到.github/ALL_BSP_COMPILE.json 详细请参考链接BSP自查

[github-actions]

👋 感谢您对 RT-Thread 的贡献！Thank you for your contribution to RT-Thread!

为确保代码符合 RT-Thread 的编码规范，请在你的仓库中执行以下步骤运行代码格式化工作流（如果格式化CI运行失败）。
To ensure your code complies with RT-Thread's coding style, please run the code formatting workflow by following the steps below (If the formatting of CI fails to run).

---

🛠 操作步骤 | Steps

1. 前往 Actions 页面 | Go to the Actions page
   点击进入工作流 → | Click to open workflow →

2. 点击 Run workflow | Click Run workflow

• 设置需排除的文件/目录（目录请以"/"结尾）
  Set files/directories to exclude (directories should end with "/")
• 将目标分支设置为 \ Set the target branch to：xmake
• 设置PR number为 \ Set the PR number to：10971

3. 等待工作流完成 | Wait for the workflow to complete
   格式化后的代码将自动推送至你的分支。
   The formatted code will be automatically pushed to your branch.

完成后，提交将自动更新至 xmake 分支，关联的 Pull Request 也会同步更新。
Once completed, commits will be pushed to the xmake branch automatically, and the related Pull Request will be updated.

如有问题欢迎联系我们，再次感谢您的贡献！💐
If you have any questions, feel free to reach out. Thanks again for your contribution!

[Copilot]

Pull request overview

This PR fixes the xmake build file generation functionality that was broken by a previous structural change. The fix correctly separates the template file from the generated output file.

• Corrects the output path for generated xmake.lua file to write to BSP directory instead of overwriting the template
• Restores the xmake.lua template file to use proper template variables instead of hardcoded values
• Ensures the template-based generation workflow functions correctly

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
tools/targets/xmake.py	Fixed output path from tools/targets/xmake.lua to current directory xmake.lua, preventing template file from being overwritten
tools/targets/xmake.lua	Restored template variables (${toolchain}, ${sdkdir}, ${src_path}, etc.) replacing hardcoded BSP-specific values that shouldn't be in the template