[rust][tools] Fix Cortex-M33 hard-float target selection

[KingingWang]

拉取/合并请求描述：(PR description)

为什么提交这份PR (why to submit this PR)

detect_rust_target() 的 Cortex-M33 分支固定返回 thumbv8m.main-none-eabi，没有使用同函数已计算的 hard_float（M4/M7 分支是判断的）。硬浮点的 M33 板卡因此拿到软浮点 ABI 的 Rust 库，链接报 uses VFP register arguments 后终止。详见 #11810。

你的解决方案是什么 (what is your solution)

按 hard_float 选择 thumbv8m.main-none-eabihf，与 M4/M7 分支保持一致。软浮点的 M33 仍走原分支，行为不变。

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

• BSP: bsp/stm32/stm32u575-st-nucleo

• .config:

CONFIG_RT_USING_RUST=y
CONFIG_RT_RUST_CORE=y
CONFIG_RUST_INIT_COMPONENT=y

• action: 本地 GCC 构建验证，fork 未启用 action

修复前：

Detected Rust target: thumbv8m.main-none-eabi
ld: error: rt-thread.elf uses VFP register arguments, build/rust/target/thumbv8m.main-none-eabi/release/librt_rust.a(...) does not
scons: *** [rt-thread.elf] Error 1

修复后：

Detected Rust target: thumbv8m.main-none-eabihf
LINK rt-thread.elf
ROM: 115100 B
scons: done building targets.

环境：rustup nightly、arm-none-eabi-gcc 14.2.1

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• 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clang-format 源码格式化工具确保格式符合RT-Thread代码规范 This PR has been formatted with clang-format and 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

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[github-actions]

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[github-actions]

📌 Code Review Assignment

🏷️ Tag: components

Reviewers: @Maihuanyi

Changed Files (Click to expand)

• components/rust/tools/build_support.py

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📊 Current Review Status (Last Updated: 2026-09-18 20:31 CST)

• ⌛ @Maihuanyi Pending Review

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