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

[Baranov Victor via cfe-commits]

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

Same here

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