[llvm] [Windows][test] Fix "LLVM" test failures when LLVM_WINDOWS_PREFER_FORWARD_SLASH is ON (PR #184556)

[Junji Watanabe via llvm-commits]

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@@ -23,13 +23,13 @@
 
 
 
-# HTML-TOP: coverage\index.html
+# HTML-TOP: coverage{{[/\\]}}index.html
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Jwata wrote:

Thank you for you for your confirmation. I updated this patch to skip this test as `directory_coverage.win.test` intentionally tests backslashes.

Please let me know if it's better to merge them.

https://github.com/llvm/llvm-project/pull/184556