trim-paths mixes forward and backslashes in backtrace when built on WIndows

Problem

trim-paths mixes forward and backslashes in backtrace when building on Windows

Expectation

Backtrace contains valid paths

Actual

Backtrace contains invalid paths mixing forward and backslashes (e.g. /path/to\file)

Steps

On a Windows machine, run command cargo new reproduce-trim-paths-mixed-slash
Paste the following in the generated Cargo.toml:
```
cargo-features = ["trim-paths"]
```

[package] name = "reproduce-trim-paths-mixed-slash" version = "0.1.0" edition = "2021"

[profile.release] debug = true trim-paths = "all"

3. Paste the following in the geenrated `src/main.rs`:

fn main() { panic!("PANICKING"); }

4. Run command `cargo build --release`
5. Run command `RUST_BACKTRACE=1 ./target/release/reproduce-trim-paths-mixed-slash.exe` (note: although I'm using Windows, my application build is Linux x86_64, and the path issue is present there too).

Output:

thread 'main' panicked at src/main.rs:2:5: PANICKING stack backtrace: 0: std::panicking::begin_panic_handler at /rustc/80eb5a8e910e5185d47cdefe3732d839c78a5e7e\library/std\src\panicking.rs:662 1: core::panicking::panic_fmt at /rustc/80eb5a8e910e5185d47cdefe3732d839c78a5e7e\library/core\src\panicking.rs:74 2: ImageBase 3: ImageBase 4: __ImageBase 5: std::rt::lang_start_internal::closure$2 at /rustc/80eb5a8e910e5185d47cdefe3732d839c78a5e7e\library/std\src\rt.rs:143 6: std::panicking::try::do_call at /rustc/80eb5a8e910e5185d47cdefe3732d839c78a5e7e\library/std\src\panicking.rs:554 7: std::panicking::try at /rustc/80eb5a8e910e5185d47cdefe3732d839c78a5e7e\library/std\src\panicking.rs:518 8: std::panic::catch_unwind at /rustc/80eb5a8e910e5185d47cdefe3732d839c78a5e7e\library/std\src\panic.rs:345 9: std::rt::lang_start_internal at /rustc/80eb5a8e910e5185d47cdefe3732d839c78a5e7e\library/std\src\rt.rs:143 10: main 11: invoke_main at D:\a_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:78 12: __scrt_common_main_seh at D:\a_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288 13: BaseThreadInitThunk 14: RtlUserThreadStart note: Some details are omitted, run with RUST_BACKTRACE=full for a verbose backtrace.


### Possible Solution(s)

Use consistent slashes in all paths

### Notes

_No response_

### Version

```text
cargo 1.82.0-nightly (0d8d22f83 2024-08-08)
release: 1.82.0-nightly
commit-hash: 0d8d22f83b066503f6b2b755925197e959e58b4f
commit-date: 2024-08-08
host: x86_64-pc-windows-msvc
libgit2: 1.8.1 (sys:0.19.0 vendored)
libcurl: 8.9.0-DEV (sys:0.4.74+curl-8.9.0 vendored ssl:Schannel)
os: Windows 10.0.22631 (Windows 11 Core) [64-bit]

Thanks for the report. I am not sure if rustc starts using -Ztrim-paths to sanitize backtrace. Could you pick a toolchain version prior to -Ztrim-paths and try if it can be reproduced? 1.74 should be sufficient.

Besides, I am not sure if we want to have backslashes for /rustc/80eb5a8e910e5185d47cdefe3732d839c78a5e7e. While it is visual consistent if using the same kind of slashes, /rustc/<hash> is in fact just a placeholder not an actual file system path, so shouldn't have impact more than visual pleasing. Doing it that might be harder for user/tool to find-and-replace the prefix. (I am not sure about the acutal use case though)

cc @michaelwoerister Kindly asking for your opinions :)

rust-lang / cargo