[clang] [llvm] [CMake] Detect properly new linker introduced in Xcode 15 (PR #77806)

[Eric Miotto via cfe-commits]

https://github.com/edymtt updated https://github.com/llvm/llvm-project/pull/77806

>From 1530d4c137642715d11b5b8b8e2aefcb7566d7c9 Mon Sep 17 00:00:00 2001
From: Eric Miotto <emiotto at apple.com>
Date: Thu, 18 Jan 2024 15:22:35 -0800
Subject: [PATCH] [CMake] Detect properly new linker introduced in Xcode 15

As explained in [1], this linker is functionally equivalent to the
classic one (`ld64`) for build system purposes -- in particular to
enable the use of order files to link `clang`.
For this reason, in addition to fixing the detection rename
`LLVM_LINKER_IS_LD64` to `LLVM_LINKER_IS_APPLE` to make the result of
such detection more clear -- this should not cause any issue to
downstream users, from a quick serch in
Sourcegraph [2], only Swift uses the value of this variable (which I
will take care of updating in due time).

[1]:
https://developer.apple.com/documentation/xcode-release-notes/xcode-15-release-notes#Linking
[2]:
https://sourcegraph.com/search?q=context:global+LLVM_LINKER_IS_LD64+lang:cmake+fork:no+-file:AddLLVM.cmake+-file:clang/tools/driver/CMakeLists.txt&patternType=standard&sm=1&groupBy=repo
rdar://120740222
---
 clang/tools/driver/CMakeLists.txt | 4 ++--
 llvm/cmake/modules/AddLLVM.cmake  | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/clang/tools/driver/CMakeLists.txt b/clang/tools/driver/CMakeLists.txt
index 2182486f93a555..d70b92b0984e52 100644
--- a/clang/tools/driver/CMakeLists.txt
+++ b/clang/tools/driver/CMakeLists.txt
@@ -103,10 +103,10 @@ if (APPLE)
 endif()
 
 if(CLANG_ORDER_FILE AND
-    (LLVM_LINKER_IS_LD64 OR LLVM_LINKER_IS_GOLD OR LLVM_LINKER_IS_LLD))
+    (LLVM_LINKER_IS_APPLE OR LLVM_LINKER_IS_GOLD OR LLVM_LINKER_IS_LLD))
   include(LLVMCheckLinkerFlag)
 
-  if (LLVM_LINKER_IS_LD64 OR (LLVM_LINKER_IS_LLD AND APPLE))
+  if (LLVM_LINKER_IS_APPLE OR (LLVM_LINKER_IS_LLD AND APPLE))
     set(LINKER_ORDER_FILE_OPTION "-Wl,-order_file,${CLANG_ORDER_FILE}")
   elseif (LLVM_LINKER_IS_GOLD)
     set(LINKER_ORDER_FILE_OPTION "-Wl,--section-ordering-file,${CLANG_ORDER_FILE}")
diff --git a/llvm/cmake/modules/AddLLVM.cmake b/llvm/cmake/modules/AddLLVM.cmake
index 14c0837c35964d..5e989618552824 100644
--- a/llvm/cmake/modules/AddLLVM.cmake
+++ b/llvm/cmake/modules/AddLLVM.cmake
@@ -211,10 +211,10 @@ if (NOT DEFINED LLVM_LINKER_DETECTED AND NOT WIN32)
     )
 
   if(APPLE)
-    if("${stderr}" MATCHES "PROJECT:ld64")
+    if("${stderr}" MATCHES "PROGRAM:ld")
       set(LLVM_LINKER_DETECTED YES CACHE INTERNAL "")
-      set(LLVM_LINKER_IS_LD64 YES CACHE INTERNAL "")
-      message(STATUS "Linker detection: ld64")
+      set(LLVM_LINKER_IS_APPLE YES CACHE INTERNAL "")
+      message(STATUS "Linker detection: Apple")
     elseif("${stderr}" MATCHES "^LLD" OR
            "${stdout}" MATCHES "^LLD")
       set(LLVM_LINKER_DETECTED YES CACHE INTERNAL "")