Targets should not depend on protobuf when enable_protobuf=0.

webrtc/modules/audio_coding/main/acm2/audio_coding_module.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.
 
 {
   'variables': {
@@ skipping 61 matching lines @@
         'codec_manager.h',
         'codec_owner.cc',
         'codec_owner.h',
         'initial_delay_manager.cc',
         'initial_delay_manager.h',
         'nack.cc',
         'nack.h',
       ],
     },
     {
-      'target_name': 'acm_dump_proto',
-      'type': 'static_library',
-      'sources': ['dump.proto',],
-      'variables': {
-        'proto_in_dir': '.',
-        # Workaround to protect against gyp's pathname relativization when
-        # this file is included by modules.gyp.
-        'proto_out_protected': 'webrtc/audio_coding',
-        'proto_out_dir': '<(proto_out_protected)',
-      },
-      'includes': ['../../../../build/protoc.gypi',],
-    },
-    {
       'target_name': 'acm_dump',
       'type': 'static_library',
       'conditions': [
         ['enable_protobuf==1', {
           'defines': ['RTC_AUDIOCODING_DEBUG_DUMP'],
+          'dependencies': ['acm_dump_proto'],
           }
         ],
       ],
       'sources': [
         'acm_dump.h',
         'acm_dump.cc'
       ],
-      'dependencies': ['acm_dump_proto'],
     },
   ],
   'conditions': [
+    ['enable_protobuf==1', {
+      'targets': [
+        {
+          'target_name': 'acm_dump_proto',
+          'type': 'static_library',
+          'sources': ['dump.proto',],
+          'variables': {
+            'proto_in_dir': '.',
+            # Workaround to protect against gyp's pathname relativization when
+            # this file is included by modules.gyp.
+            'proto_out_protected': 'webrtc/audio_coding',
+            'proto_out_dir': '<(proto_out_protected)',
+          },
+          'includes': ['../../../../build/protoc.gypi',],
+        },
+      ]
+    }],
     ['include_tests==1', {
       'targets': [
         {
           'target_name': 'acm_receive_test',
           'type': 'static_library',
           'defines': [
             '<@(audio_coding_defines)',
           ],
           'dependencies': [
             '<@(audio_coding_dependencies)',
@@ skipping 61 matching lines @@
           'sources': [
              '../test/insert_packet_with_timing.cc',
              '../test/Channel.cc',
              '../test/PCMFile.cc',
            ],
         }, # delay_test
       ],
     }],
   ],
 }