[llvm] [CI] Enable -Werror on Windows (PR #210607)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 created https://github.com/llvm/llvm-project/pull/210607

We use a recent clang-cl based toolchain which should be expected to build clang cleanly on Windows

>From 6224b4de79463603e3d77b5a3f40a4ec1396ee46 Mon Sep 17 00:00:00 2001
From: Aiden Grossman <aidengrossman at google.com>
Date: Sun, 19 Jul 2026 16:08:23 +0000
Subject: [PATCH] [CI] Enable -Werror on Windows

We use a recent clang-cl based toolchain which should be expected to build
clang cleanly on Windows
---
 .ci/monolithic-windows.sh | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.ci/monolithic-windows.sh b/.ci/monolithic-windows.sh
index 67cbebb1beb5c..080a6a05149aa 100755
--- a/.ci/monolithic-windows.sh
+++ b/.ci/monolithic-windows.sh
@@ -57,6 +57,7 @@ cmake -S "${MONOREPO_ROOT}"/llvm -B "${BUILD_DIR}" \
       -D CMAKE_MODULE_LINKER_FLAGS="/MANIFEST:NO" \
       -D CMAKE_SHARED_LINKER_FLAGS="/MANIFEST:NO" \
       -D LLVM_ENABLE_RUNTIMES="${runtimes}" \
+      -D LLVM_ENABLE_WERROR=ON \
       "${runtime_cmake_args[@]}"
 
 start-group "ninja"