[clang] Fix MSVC build after #206326 (PR #206993)

[Corentin Jabot via cfe-commits]

https://github.com/cor3ntin created https://github.com/llvm/llvm-project/pull/206993

None

>From 2d6c42de0af5d4849b1bd22f09a4cfbf219501b6 Mon Sep 17 00:00:00 2001
From: Corentin Jabot <corentinjabot at gmail.com>
Date: Wed, 1 Jul 2026 16:02:15 +0200
Subject: [PATCH] Fix NSVC build after #206326

---
 clang/unittests/Basic/CMakeLists.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/clang/unittests/Basic/CMakeLists.txt b/clang/unittests/Basic/CMakeLists.txt
index 058243fd3fdba..016b6d5ddcb7b 100644
--- a/clang/unittests/Basic/CMakeLists.txt
+++ b/clang/unittests/Basic/CMakeLists.txt
@@ -21,3 +21,4 @@ add_distinct_clang_unittest(BasicTests
   Support
   TargetParser
   )
+target_compile_options(BasicTests PRIVATE "$<$<CXX_COMPILER_ID:MSVC>:/utf-8>")