From e99f3e887ef98a5c5764c40d57b218bbdb1e144b Mon Sep 17 00:00:00 2001
From: Anthony Latsis <alatsis@apple.com>
Date: Thu, 19 Jun 2025 04:10:01 +0100
Subject: [PATCH] [presets] Actually make
 https://github.com/swiftlang/swift/pull/81284 work

---
 CMakeLists.txt          | 3 +++
 utils/build-presets.ini | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index e76ce7d0f9f92..a6a0d22bbf6c3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -824,6 +824,9 @@ elseif(UNIX)
   include(UnixCompileRules)
 endif()
 
+# Add any extra C++ compilation options that were passed down.
+add_compile_options($<$<COMPILE_LANGUAGE:CXX>:${SWIFT_EXTRA_CXX_FLAGS}>)
+
 if(CMAKE_C_COMPILER_ID MATCHES Clang)
   add_compile_options($<$<OR:$<COMPILE_LANGUAGE:C>,$<COMPILE_LANGUAGE:CXX>>:-Werror=gnu>)
 endif()
diff --git a/utils/build-presets.ini b/utils/build-presets.ini
index fc28757ed7449..992ceb2e4d0f9 100644
--- a/utils/build-presets.ini
+++ b/utils/build-presets.ini
@@ -681,7 +681,7 @@ enable-new-runtime-build
 
 # Escalate certain C++ warnings to errors for Swift.
 extra-swift-cmake-options=
-   -DCMAKE_CXX_FLAGS="-Werror=unused"
+   -DSWIFT_EXTRA_CXX_FLAGS="-Werror=unused"
 
 [preset: buildbot_incremental,tools=RA,stdlib=RD,smoketest=macosx,flto]
 mixin-preset=buildbot_incremental,tools=RA,stdlib=RD,smoketest=macosx