Enabled -fsanitize-address-use-after-scope for -DLLVM_USE_SANITIZER=Address

llvm/trunk/cmake/modules/HandleLLVMOptions.cmake

if (LLVM_USE_SANITIZER STREQUAL "Address")
       append_common_sanitizer_flags()
       append("-fsanitize=address" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
     else()
       message(FATAL_ERROR "This sanitizer not yet supported in the MSVC environment: ${LLVM_USE_SANITIZER}")
     endif()
   else()
     message(FATAL_ERROR "LLVM_USE_SANITIZER is not supported on this platform.")
   endif()
+  if (LLVM_USE_SANITIZER MATCHES "(Undefined;)?Address(;Undefined)?")
+    append("-fsanitize-address-use-after-scope" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+  endif()
   if (LLVM_USE_SANITIZE_COVERAGE)
     append("-fsanitize-coverage=trace-pc-guard,indirect-calls,trace-cmp" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
   endif()
 endif()
 
 # Turn on -gsplit-dwarf if requested
 if(LLVM_USE_SPLIT_DWARF)
   add_definitions("-gsplit-dwarf")