Linux: fix build when libgcrypt is not installed.

build/linux/system.gyp

 # Copyright (c) 2011 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.
 
 {
   'conditions': [
     ['sysroot!=""', {
       'variables': {
         'pkg-config': './pkg-config-wrapper "<(sysroot)"',
       },
@@ skipping 296 matching lines @@
             'libraries': [
               '<!@(<(pkg-config) --libs-only-l xext)',
             ],
           },
       }]]
     },
     {
       'target_name': 'libgcrypt',
       'type': 'settings',
       'conditions': [
-        ['_toolset=="target"', {
+        ['_toolset=="target" and use_cups==1', {
           'direct_dependent_settings': {
             'cflags': [
               '<!@(libgcrypt-config --cflags)',
             ],
           },
           'link_settings': {
             'libraries': [
               '<!@(libgcrypt-config --libs)',
             ],
           },
@@ skipping 96 matching lines @@
             ],
             'libraries': [
               '<!@(<(pkg-config) --libs-only-l "ibus-1.0 >= <(ibus_min_version)")',
             ],
           },
         }],
       ],
     },
   ],
 }