Imported Upstream version 5.18.0.205

Former-commit-id: 7f59f7e792705db773f1caecdaa823092f4e2927

external/llvm/cmake/modules/HandleLLVMStdlib.cmake

@@ -0,0 +1,30 @@
+# This CMake module is responsible for setting the standard library to libc++
+# if the user has requested it.
+
+include(DetermineGCCCompatible)
+
+if(NOT DEFINED LLVM_STDLIB_HANDLED)
+  set(LLVM_STDLIB_HANDLED ON)
+
+  function(append value)
+    foreach(variable ${ARGN})
+      set(${variable} "${${variable}} ${value}" PARENT_SCOPE)
+    endforeach(variable)
+  endfunction()
+
+  include(CheckCXXCompilerFlag)
+  if(LLVM_ENABLE_LIBCXX)
+    if(LLVM_COMPILER_IS_GCC_COMPATIBLE)
+      check_cxx_compiler_flag("-stdlib=libc++" CXX_SUPPORTS_STDLIB)
+      if(CXX_SUPPORTS_STDLIB)
+        append("-stdlib=libc++"
+          CMAKE_CXX_FLAGS CMAKE_EXE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS
+          CMAKE_MODULE_LINKER_FLAGS)
+      else()
+        message(WARNING "Can't specify libc++ with '-stdlib='")
+      endif()
+    else()
+      message(WARNING "Not sure how to specify libc++ for this compiler")
+    endif()
+  endif()
+endif()