Update from https://crrev.com/320931

sandbox/linux/sandbox_linux_test_sources.gypi

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Tests need to be compiled in the same link unit, so we have to list them
 # in a separate .gypi file.
 {
   'dependencies': [
     'sandbox',
     'sandbox_linux_test_utils',
@@ skipping 44 matching lines @@
         'seccomp-bpf/syscall_unittest.cc',
       ],
     }],
     [ 'compile_credentials==1', {
       'sources': [
         'integration_tests/namespace_unix_domain_socket_unittest.cc',
         'services/credentials_unittest.cc',
         'services/namespace_sandbox_unittest.cc',
         'services/namespace_utils_unittest.cc',
       ],
+      'dependencies': [
+        '../build/linux/system.gyp:libcap'
+      ],
     }],
   ],
 }