[llvm] [Offload] Override linker for device build (PR #137246)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 created https://github.com/llvm/llvm-project/pull/137246

Summary:
Override the default linker in case the user is passing it separately.
This requires `lld` but it always did. This will be fixed *properly*
when https://github.com/llvm/llvm-project/pull/136729 lands.


>From 6021e26101feada145c4a29b4cd8d66ca8a1ba23 Mon Sep 17 00:00:00 2001
From: Joseph Huber <huberjn at outlook.com>
Date: Thu, 24 Apr 2025 14:49:32 -0500
Subject: [PATCH] [Offload] Override linker for device build

Summary:
Override the default linker in case the user is passing it separately.
This requires `lld` but it always did. This will be fixed *properly*
when https://github.com/llvm/llvm-project/pull/136729 lands.
---
 offload/DeviceRTL/CMakeLists.txt | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/offload/DeviceRTL/CMakeLists.txt b/offload/DeviceRTL/CMakeLists.txt
index b1c48cbaefe16..f8a6d8563916a 100644
--- a/offload/DeviceRTL/CMakeLists.txt
+++ b/offload/DeviceRTL/CMakeLists.txt
@@ -132,9 +132,9 @@ function(compileDeviceRTLLibrary target_name target_triple)
     BUILD_RPATH ""
     INSTALL_RPATH ""
     RUNTIME_OUTPUT_NAME libomptarget-${target_name}.bc)
-  target_compile_options(libomptarget-${target_name} PRIVATE "--target=${target_triple}" "-march=")
+  target_compile_options(libomptarget-${target_name} PRIVATE "--target=${target_triple}" "-fuse-ld=lld" "-march=")
   target_link_options(libomptarget-${target_name} PRIVATE "--target=${target_triple}"
-                      "-r" "-nostdlib" "-flto" "-Wl,--lto-emit-llvm" "-march=")
+                      "-r" "-nostdlib" "-flto" "-Wl,--lto-emit-llvm" "-fuse-ld=lld" "-march=")
   install(TARGETS libomptarget-${target_name}
           PERMISSIONS OWNER_WRITE OWNER_READ GROUP_READ WORLD_READ
           DESTINATION "lib${LLVM_LIBDIR_SUFFIX}/${target_triple}")
@@ -151,6 +151,8 @@ function(compileDeviceRTLLibrary target_name target_triple)
     LINKER_LANGUAGE CXX
   )
   target_link_libraries(omptarget.${target_name} PRIVATE omptarget.${target_name}.all_objs)
+  target_link_options(omptarget.${target_name} PRIVATE "--target=${target_triple}"
+                      "-r" "-nostdlib" "-flto" "-Wl,--lto-emit-llvm" "-fuse-ld=lld" "-march=")
 
   install(TARGETS omptarget.${target_name}
           ARCHIVE DESTINATION "lib${LLVM_LIBDIR_SUFFIX}/${target_triple}")