[LTO] Extend CAS build workaround to LTO (#20814)

Shared library build fails with the same error Jinsong saw and fixed in
e676cb0
as part of the pulldown. This was missed because we don't run the
nightly as part of the pulldown CI, and we only do a shared library
build in the nightly.

Fix confirmed in
https://github.com/intel/llvm/actions/runs/19906696122/job/57064646962

Closes: #20743

Signed-off-by: Nick Sarnie <[email protected]>

Author: sarnex

llvm/lib/LTO/CMakeLists.txt

@@ -1,3 +1,10 @@
+if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+  # We append -fno-lifetime-dse in HandleLLVMOptions.cmake
+  # append("-fno-lifetime-dse" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+  # But it is causing link failure with llvm::StdThreadPool::asyncEnqueue
+  string(REPLACE "-fno-lifetime-dse" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+endif ()
+
 add_llvm_component_library(LLVMLTO
   LTO.cpp
   LTOBackend.cpp