[libcxx] Check MSVC flag directly instead of setting LIBCXX_TARGETING_MSVC

[DavidSpickett]

Summary

MSVC is set for actual msvc and clang-cl. LIBXX_TARGETTING_CLANG_CL is
still used over in runtimes to configure warning flags.

[DavidSpickett]

Remove TARGETING_MSVC value.

[DavidSpickett]

Looking at a clang-cl build in CI I see:

_bk;t=1688719464638-- Configuring for clang-cl
_bk;t=1688719464638-- Configuring for MSVC

Which proves that MSVC is also set for clang-cl. The LIBCXX_TARGETING...

[DavidSpickett]

Remove empty else.

[ldionne]

Thanks for the cleanup!

libcxx/CMakeLists.txt

  build directory and run 'cmake /path/to/${PROJECT_NAME} [options]' there."
  )
 if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" AND "${CMAKE_CXX_SIMULATE_ID}" STREQUAL "MSVC")
   message(STATUS "Configuring for clang-cl")
   set(LIBCXX_TARGETING_CLANG_CL ON)
 endif()
 
 if (MSVC)
-  set(LIBCXX_TARGETING_MSVC ON)
   message(STATUS "Configuring for MSVC")
-else()
-  set(LIBCXX_TARGETING_MSVC OFF)
 endif()
 
 #===============================================================================
 # Setup CMake Options
 #===============================================================================
 include(CMakeDependentOption)
 include(HandleCompilerRT)
 
message(FATAL_ERROR "Value '${LIBCXX_TYPEINFO_COMPARISON_IMPLEMENTATION}' is not a valid value for
                        LIBCXX_TYPEINFO_COMPARISON_IMPLEMENTATION")
 endif()
 
 set(LIBCXX_ABI_DEFINES "" CACHE STRING "A semicolon separated list of ABI macros to define in the site config header.")
 option(LIBCXX_EXTRA_SITE_DEFINES "Extra defines to add into __config_site")
 option(LIBCXX_USE_COMPILER_RT "Use compiler-rt instead of libgcc" OFF)
 
 # ABI Library options ---------------------------------------------------------
-if (LIBCXX_TARGETING_MSVC)
+if (MSVC)
   set(LIBCXX_DEFAULT_ABI_LIBRARY "vcruntime")
 elseif (${CMAKE_SYSTEM_NAME} MATCHES "FreeBSD")
   set(LIBCXX_DEFAULT_ABI_LIBRARY "libcxxrt")
 else()
   set(LIBCXX_DEFAULT_ABI_LIBRARY "libcxxabi")
 endif()
 
 set(LIBCXX_SUPPORTED_ABI_LIBRARIES none libcxxabi system-libcxxabi libcxxrt libstdc++ libsupc++ vcruntime)
else()
     target_add_compile_flags_if_supported(${target} PUBLIC -EHs- -EHa-)
     target_add_compile_flags_if_supported(${target} PUBLIC -fno-exceptions)
   endif()
 endfunction()
 
 # RTTI flags ==================================================================
 function(cxx_add_rtti_flags target)
   if (NOT LIBCXX_ENABLE_RTTI)
-    if (LIBCXX_TARGETING_CLANG_CL OR LIBCXX_TARGETING_MSVC)
+    if (MSVC)
       target_add_compile_flags_if_supported(${target} PUBLIC -GR-)
     else()
       target_add_compile_flags_if_supported(${target} PUBLIC -fno-rtti)
     endif()
   endif()
 endfunction()
 
 # Threading flags =============================================================
 if (LIBCXX_BUILD_EXTERNAL_THREAD_LIBRARY AND LIBCXX_ENABLE_SHARED)
   # Need to allow unresolved symbols if this is to work with shared library builds
   if (APPLE)
     add_link_flags("-undefined dynamic_lookup")
   else()
     # Relax this restriction from HandleLLVMOptions
     string(REPLACE "-Wl,-z,defs" "" CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS}")
   endif()
 endif()
 
 # Assertion flags =============================================================
 define_if(LIBCXX_DEBUG_BUILD -D_DEBUG)
 if (LIBCXX_ENABLE_ASSERTIONS AND NOT LIBCXX_DEBUG_BUILD)
   # MSVC doesn't like _DEBUG on release builds. See PR 4379.
-  define_if_not(LIBCXX_TARGETING_MSVC -D_DEBUG)
+  define_if_not(MSVC -D_DEBUG)
 endif()
 
 # Modules flags ===============================================================
 # FIXME The libc++ sources are fundamentally non-modular. They need special
 # versions of the headers in order to provide C++03 and legacy ABI definitions.
 # NOTE: The public headers can be used with modules in all other contexts.
 function(cxx_add_module_flags target)
   if (LLVM_ENABLE_MODULES)
# all libraries but c++ have to be added in manually.
   if (LIBCXX_HAS_ATOMIC_LIB)
     target_link_libraries(${target} PRIVATE atomic)
   endif()
 
   if (MINGW)
     target_link_libraries(${target} PRIVATE "${MINGW_LIBRARIES}")
   endif()
 
-  if (LIBCXX_TARGETING_MSVC)
+  if (MSVC)
     if (LIBCXX_DEBUG_BUILD)
       set(LIB_SUFFIX "d")
     else()
       set(LIB_SUFFIX "")
     endif()
 
     target_link_libraries(${target} PRIVATE ucrt${LIB_SUFFIX}) # Universal C runtime
     target_link_libraries(${target} PRIVATE vcruntime${LIB_SUFFIX}) # C++ runtime