Re-enable LLVM LTO on Neon targets.

webrtc/build/arm_neon.gypi

 # Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 # This file sets correct neon flags. Include it if you want to build
 # source with neon intrinsics.
@@ skipping 12 matching lines @@
   'cflags!': [
     '-mfpu=vfpv3-d16',
   ],
   'conditions': [
     # "-mfpu=neon" is not required for arm64 in GCC.
     ['target_arch!="arm64"', {
       'cflags': [
         '-mfpu=neon',
        ],
     }],
-    # Disable LTO on NEON targets due to compiler bug.
+    # Disable GCC LTO on NEON targets due to compiler bug.
     # TODO(fdegans): Enable this. See crbug.com/408997.
-    ['use_lto==1', {
+    ['clang==0 and use_lto==1', {
       'cflags!': [
         '-flto',
         '-ffat-lto-objects',
       ],
     }],
   ],
 }