libunwind is not excluded on android-clang builds

# STL specific flags.
set(ANDROID_STL_PATH "${ANDROID_NDK}/sources/cxx-stl/llvm-libc++")
if(ANDROID_STL STREQUAL system)
  set(CMAKE_CXX_STANDARD_INCLUDE_DIRECTORIES
    "${ANDROID_NDK}/sources/cxx-stl/system/include")
elseif(ANDROID_STL MATCHES "^c\\+\\+_")
  if(ANDROID_ABI MATCHES "^armeabi")
    list(APPEND ANDROID_LINKER_FLAGS -Wl,--exclude-libs,libunwind.a)
  endif()

  list(APPEND ANDROID_COMPILER_FLAGS_CXX -std=c++11)

  # Add the libc++ lib directory to the path so the linker scripts can pick up
  # the extra libraries.
  list(APPEND ANDROID_LINKER_FLAGS
    "-L${ANDROID_STL_PATH}/libs/${ANDROID_ABI}")

  set(CMAKE_CXX_STANDARD_INCLUDE_DIRECTORIES "${ANDROID_STL_PATH}/include")

  if(ANDROID_PLATFORM_LEVEL LESS 21)
    set(CMAKE_CXX_STANDARD_INCLUDE_DIRECTORIES
      "${CMAKE_CXX_STANDARD_INCLUDE_DIRECTORIES}"
      "${ANDROID_NDK}/sources/android/support/include")
  endif()

  set(CMAKE_CXX_STANDARD_INCLUDE_DIRECTORIES
    "${CMAKE_CXX_STANDARD_INCLUDE_DIRECTORIES}"
    "${ANDROID_STL_PATH}abi/include")
endif()