[ROCm][Windows] Fix LoadHIP handling of environment variable paths.

[ScottTodd]

See https://cmake.org/cmake/help/latest/command/file.html#path-conversion. Paths stored in environment variables may use / or \ (e.g. on Windows), while cmake-style paths always use /.

This fixes configure errors like:

CMake Error at D:/b/audio_main/build/temp.win-amd64-cpython-312/Release/CMakeFiles/CMakeScratch/TryCompile-y9h2qt/CMakeLists.txt:2 (set): Syntax error in cmake code at D:/b/audio_main/build/temp.win-amd64-cpython-312/Release/CMakeFiles/CMakeScratch/TryCompile-y9h2qt/CMakeLists.txt:2 when parsing string D:/projects/TheRock/external-builds/pytorch/.venv/Lib/site-packages/_rocm_sdk_devel/cmake/;D:\projects\TheRock\external-builds\pytorch\.venv\Lib\site-packages\_rocm_sdk_devel/lib/cmake/hip;D:/b/audio_main/cmake Invalid character escape '\p'. 

(note the mixed usage of \ and / in that string)

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/audio/3991

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❌ 7 New Failures, 15 Pending

As of commit d62c3a1 with merge base 46b5dc6 ():

NEW FAILURES - The following jobs have failed:

• .github/workflows/bandit.yml (gh)
• .github/workflows/integration-test.yml (gh)
• .github/workflows/lint.yml (gh)
• .github/workflows/pr-labels.yml (gh)
• .github/workflows/unittest-macos-cpu.yml (gh)
• .github/workflows/unittest-windows-cpu.yml (gh)
• .github/workflows/unittest-windows-gpu.yml (gh)

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[ScottTodd]

cc @jeffdaily @jithunnair-amd @pruthvistony

[jeffdaily]

I approve, but I don't have any real authority in this torchaudio repo.

[ScottTodd]

Thanks. Do you know who we should ask then? Looks like most commit activity in the last few months (https://github.com/pytorch/audio/graphs/contributors?from=5%2F10%2F2025) has been from @samanklesaria

[atalman]

cc @NicolasHug

[jammm]

cc @NicolasHug

@NicolasHug would appreciate your review here :)