[cmake] switch to CMake's native check_compiler_flag, delete LLVMCheckCompilerLinkerFlag.cmake

now that CMake baseline has moved past 3.19; see
https://cmake.org/cmake/help/latest/module/CheckCompilerFlag.html

Co-Authored-By: Ryan Prichard <[email protected]>

Author: h-vetinari

clang/tools/clang-repl/CMakeLists.txt

@@ -69,7 +69,7 @@ export_executable_symbols_for_plugins(clang-repl)
 # gold. This flag tells the linker to build a PLT for the full address range.
 # Linkers without this flag are assumed to support proper PLTs by default.
 set(flag_long_plt "-Wl,--long-plt")
-llvm_check_linker_flag(CXX ${flag_long_plt} HAVE_LINKER_FLAG_LONG_PLT)
+check_linker_flag(CXX ${flag_long_plt} HAVE_LINKER_FLAG_LONG_PLT)
 if(HAVE_LINKER_FLAG_LONG_PLT)
   target_link_options(clang-repl PRIVATE ${flag_long_plt})
 endif()

cmake/Modules/LLVMCheckCompilerLinkerFlag.cmake

@@ -1,14 +1,8 @@
 include(CMakePushCheckState)
-
-include(CheckCompilerFlag OPTIONAL)
-
-if(NOT COMMAND check_compiler_flag)
-  include(CheckCCompilerFlag)
-  include(CheckCXXCompilerFlag)
-endif()
+include(CheckCompilerFlag)
 
 function(llvm_check_compiler_linker_flag lang flag out_var)
-  # If testing a flag with check_c_compiler_flag, it gets added to the compile
+  # If testing a flag with check_compiler_flag, it gets added to the compile
   # command only, but not to the linker command in that test. If the flag
   # is vital for linking to succeed, the test would fail even if it would
   # have succeeded if it was included on both commands.
@@ -18,18 +12,6 @@ function(llvm_check_compiler_linker_flag lang flag out_var)
 
   cmake_push_check_state()
   set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} ${flag}")
-  if(COMMAND check_compiler_flag)
-    check_compiler_flag("${lang}" "" ${out_var})
-  else()
-    # Until the minimum CMAKE version is 3.19
-    # cmake builtin compatible, except we assume lang is C or CXX
-    if("${lang}" STREQUAL "C")
-      check_c_compiler_flag("" ${out_var})
-    elseif("${lang}" STREQUAL "CXX")
-      check_cxx_compiler_flag("" ${out_var})
-    else()
-      message(FATAL_ERROR "\"${lang}\" is not C or CXX")
-    endif()
-  endif()
+  check_compiler_flag("${lang}" "" ${out_var})
   cmake_pop_check_state()
 endfunction()

compiler-rt/cmake/config-ix.cmake

@@ -1,6 +1,5 @@
 include(CMakePushCheckState)
 include(AddLLVM)
-include(LLVMCheckCompilerLinkerFlag)
 include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
 include(CheckIncludeFiles)
@@ -15,7 +14,7 @@ include(TestBigEndian)
 # in tree version of runtimes, we'd be linking against the just-built
 # libunwind (and the compiler implicit -lunwind wouldn't succeed as the newly
 # built libunwind isn't installed yet). For those cases, it'd be good to
-# link with --uwnindlib=none. Check if that option works.
+# link with --unwindlib=none. Check if that option works.
 llvm_check_compiler_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_NONE_FLAG)
 
 check_library_exists(c fopen "" COMPILER_RT_HAS_LIBC)

libcxx/cmake/config-ix.cmake

@@ -12,7 +12,7 @@ include(CheckCSourceCompiles)
 # LIBCXXABI_USE_LLVM_UNWINDER set, we'd be linking against the just-built
 # libunwind (and the compiler implicit -lunwind wouldn't succeed as the newly
 # built libunwind isn't installed yet). For those cases, it'd be good to
-# link with --uwnindlib=none. Check if that option works.
+# link with --unwindlib=none. Check if that option works.
 llvm_check_compiler_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_EQ_NONE_FLAG)
 
 if (NOT LIBCXX_USE_COMPILER_RT)