Linux: clean up the usage of "use_cups" gyp switch:

build/linux/system.gyp

 # Copyright (c) 2009 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 252 matching lines @@
             'ldflags': [
               '<!@(<(pkg-config) --libs-only-L --libs-only-other xext)',
             ],
             'libraries': [
               '<!@(<(pkg-config) --libs-only-l xext)',
             ],
           },
       }]]
     },
     {
+      'target_name': 'libgcrypt',
+      'type': 'settings',
+      'conditions': [
+        ['_toolset=="target"', {
+          'direct_dependent_settings': {
+            'cflags': [
+              '<!@(libgcrypt-config --cflags)',
+            ],
+          },
+          'link_settings': {
+            'libraries': [
+              '<!@(libgcrypt-config --libs)',
+            ],
+          },
+      }]]
+    },
+    {
       'target_name': 'selinux',
       'type': 'settings',
       'conditions': [
         ['_toolset=="target"', {
           'link_settings': {
             'libraries': [
               '-lselinux',
             ],
           },
       }]]
@@ skipping 88 matching lines @@
       ],
     },
   ],
 }
 
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