[clang] [clang][Lex] warn on backslashes in include paths (PR #186770)

[Aaron Ballman via cfe-commits]

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@@ -0,0 +1,14 @@
+// REQUIRES: system-windows
+// RUN: mkdir -p %t/backslash
+// RUN: cp %S/Inputs/case-insensitive-include.h %t/backslash/case-insensitive-include.h
+// RUN: %clang -fsyntax-only -I%t %s 2>&1 | FileCheck %s
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AaronBallman wrote:

This should be running `%clang_cc1` and not `%clang`.

https://github.com/llvm/llvm-project/pull/186770