[clang-tools-extra] [clang-tidy] Normalize windows line filter paths (PR #217038)

[Chris Apple via cfe-commits]

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@@ -75,6 +75,16 @@ TEST(ParseLineFilter, ValidFilter) {
   EXPECT_EQ(1000u, Options.LineFilter[2].LineRanges[0].second);
 }
 
+#ifdef _WIN32
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cjappl wrote:

see above

https://github.com/llvm/llvm-project/pull/217038