[clang] [CMake][Release] Build with -ffat-lto-objects (PR #140381)

[Tom Stellard via cfe-commits]

https://github.com/tstellar created https://github.com/llvm/llvm-project/pull/140381

Fixes #133580

>From abf0d25f2197cb154ec7afd7bca5962975742b44 Mon Sep 17 00:00:00 2001
From: Tom Stellard <tstellar at redhat.com>
Date: Sat, 17 May 2025 16:40:51 +0000
Subject: [PATCH] [CMake][Release] Build with -ffat-lto-objects

Fixes #133580
---
 clang/cmake/caches/Release.cmake | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/clang/cmake/caches/Release.cmake b/clang/cmake/caches/Release.cmake
index fb12dfcdcb5a5..592829e01206d 100644
--- a/clang/cmake/caches/Release.cmake
+++ b/clang/cmake/caches/Release.cmake
@@ -102,7 +102,7 @@ if (LLVM_RELEASE_ENABLE_LTO)
   # FIXME: We can't use LLVM_ENABLE_LTO=Thin here, because it causes the CMake
   # step for the libcxx build to fail.  CMAKE_INTERPROCEDURAL_OPTIMIZATION does
   # enable ThinLTO, though.
-  set(RUNTIMES_CMAKE_ARGS "-DCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON -DLLVM_ENABLE_LLD=ON" CACHE STRING "")
+  set(RUNTIMES_CMAKE_ARGS "-DCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON -DLLVM_ENABLE_LLD=ON -DLLVM_ENABLE_FATLTO=ON" CACHE STRING "")
 endif()
 
 # Stage 1 Common Config
@@ -144,3 +144,6 @@ set_final_stage_var(CPACK_GENERATOR "TXZ" STRING)
 set_final_stage_var(CPACK_ARCHIVE_THREADS "0" STRING)
 
 set_final_stage_var(LLVM_USE_STATIC_ZSTD "ON" BOOL)
+if (LLVM_RELEASE_ENABLE_LTO)
+  set_final_stage_var(LLVM_ENABLE_FATLTO "ON" BOOL)
+endif()