[libunwind] [llvm] [runtimes] remove workaround for old CMake when setting `--unwindlib=none` (PR #93429)

[via llvm-commits]

https://github.com/h-vetinari updated https://github.com/llvm/llvm-project/pull/93429

>From 8c1b899aa174b107fece1edbf99eaf261bdea516 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Storsj=C3=B6?= <martin at martin.st>
Date: Mon, 25 Apr 2022 09:45:22 +0300
Subject: [PATCH] [runtimes] [CMake] Use CMAKE_REQUIRED_LINK_OPTIONS to
 simplify handling of the --unwindlib=none option

This avoids passing the option unnecessarily to compilation commands
(where it causes warnings).

This fails in practice with libunwind, where setting
CMAKE_TRY_COMPILE_TARGET_TYPE to STATIC_LIBRARY breaks it, as
the option from CMAKE_REQUIRED_LINK_OPTIONS ends up passed to the "ar"
tool too.
---
 libunwind/CMakeLists.txt |  3 +++
 runtimes/CMakeLists.txt  | 22 +---------------------
 2 files changed, 4 insertions(+), 21 deletions(-)

diff --git a/libunwind/CMakeLists.txt b/libunwind/CMakeLists.txt
index b22ade0a7d71e..3d2fadca9d2ec 100644
--- a/libunwind/CMakeLists.txt
+++ b/libunwind/CMakeLists.txt
@@ -221,9 +221,12 @@ add_cxx_compile_flags_if_supported(-EHsc)
 # This leads to libunwind not being built with this flag, which makes
 # libunwind quite useless in this setup.
 set(_previous_CMAKE_TRY_COMPILE_TARGET_TYPE ${CMAKE_TRY_COMPILE_TARGET_TYPE})
+set(_previous_CMAKE_REQUIRED_LINK_OPTIONS ${CMAKE_REQUIRED_LINK_OPTIONS})
 set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
+set(CMAKE_REQUIRED_LINK_OPTIONS)
 add_compile_flags_if_supported(-funwind-tables)
 set(CMAKE_TRY_COMPILE_TARGET_TYPE ${_previous_CMAKE_TRY_COMPILE_TARGET_TYPE})
+set(CMAKE_REQUIRED_LINK_OPTIONS ${_previous_CMAKE_REQUIRED_LINK_OPTIONS})
 
 if (LIBUNWIND_USES_ARM_EHABI AND NOT CXX_SUPPORTS_FUNWIND_TABLES_FLAG)
   message(SEND_ERROR "The -funwind-tables flag must be supported "
diff --git a/runtimes/CMakeLists.txt b/runtimes/CMakeLists.txt
index 24f4851169591..8f909322c9a98 100644
--- a/runtimes/CMakeLists.txt
+++ b/runtimes/CMakeLists.txt
@@ -116,27 +116,7 @@ filter_prefixed("${CMAKE_ASM_IMPLICIT_INCLUDE_DIRECTORIES}" ${LLVM_BINARY_DIR} C
 # brittle. We should ideally move this to runtimes/CMakeLists.txt.
 llvm_check_compiler_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_EQ_NONE_FLAG)
 if (CXX_SUPPORTS_UNWINDLIB_EQ_NONE_FLAG)
-  set(ORIG_CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS}")
-  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} --unwindlib=none")
-  # TODO: When we can require CMake 3.14, we should use
-  # CMAKE_REQUIRED_LINK_OPTIONS here. Until then, we need a workaround:
-  # When using CMAKE_REQUIRED_FLAGS, this option gets added both to
-  # compilation and linking commands. That causes warnings in the
-  # compilation commands during cmake tests. This is normally benign, but
-  # when testing whether -Werror works, that test fails (due to the
-  # preexisting warning).
-  #
-  # Therefore, before we can use CMAKE_REQUIRED_LINK_OPTIONS, check if we
-  # can use --start-no-unused-arguments to silence the warnings about
-  # --unwindlib=none during compilation.
-  #
-  # We must first add --unwindlib=none to CMAKE_REQUIRED_FLAGS above, to
-  # allow this subsequent test to succeed, then rewrite CMAKE_REQUIRED_FLAGS
-  # below.
-  check_c_compiler_flag("--start-no-unused-arguments" C_SUPPORTS_START_NO_UNUSED_ARGUMENTS)
-  if (C_SUPPORTS_START_NO_UNUSED_ARGUMENTS)
-    set(CMAKE_REQUIRED_FLAGS "${ORIG_CMAKE_REQUIRED_FLAGS} --start-no-unused-arguments --unwindlib=none --end-no-unused-arguments")
-  endif()
+  list(APPEND CMAKE_REQUIRED_LINK_OPTIONS "--unwindlib=none")
 endif()
 
 # Disable use of the installed C++ standard library when building runtimes.