[llvm] Normalize file path to fix problems with different folder separators. (PR #215225)

[James Henderson via llvm-commits]

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@@ -151,3 +151,36 @@
 ; LINE-SUBST-PREFIX-NEXT: pushq
 ; LINE-SUBST-PREFIX: ; [[PREFIX]]{{[/\\]}}Inputs{{[/\\]}}source-interleave-x86_64.c:3
 ; LINE-SUBST-PREFIX-NEXT: movq
+
+;; Objects built on Windows record source paths with '\' separators, which are
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jh7370 wrote:

I'd add a "may" before "record", since a LLVM_WINDOWS_PREFER_FORWARD_SLASH would presumably result in a forward slash being used in the built file.

https://github.com/llvm/llvm-project/pull/215225