Linux: add GYP flag to build with system libbz2.

third_party/bzip2/bzip2.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.
 
 {
   'includes': [
     '../../build/common.gypi',
   ],
-  'targets': [
-    {
-      'target_name': 'bzip2',
-      'type': '<(library)',
-      'defines': ['BZ_NO_STDIO'],
-      'msvs_guid': '2A70CBF0-847E-4E3A-B926-542A656DC7FE',
-      'sources': [
-        'blocksort.c',
-        'bzlib.c',
-        'bzlib.h',
-        'bzlib_private.h',
-        'compress.c',
-        'crctable.c',
-        'decompress.c',
-        'huffman.c',
-        'randtable.c',
+  'variables': {
+    'use_system_bzip2%': 0,
+  },
+  'conditions': [
+    ['use_system_bzip2==0', {
+      'targets': [
+        {
+          'target_name': 'bzip2',
+          'type': '<(library)',
+          'defines': ['BZ_NO_STDIO'],
+          'msvs_guid': '2A70CBF0-847E-4E3A-B926-542A656DC7FE',
+          'sources': [
+            'blocksort.c',
+            'bzlib.c',
+            'bzlib.h',
+            'bzlib_private.h',
+            'compress.c',
+            'crctable.c',
+            'decompress.c',
+            'huffman.c',
+            'randtable.c',
+          ],
+          'direct_dependent_settings': {
+            'include_dirs': [
+              '.',
+            ],
+          },
+          'conditions': [
+            ['OS=="win"', {
+              'product_name': 'libbzip2',
+            }, {  # else: OS!="win"
+              'product_name': 'bz2',
+            }],
+          ],
+        },
       ],
-      'direct_dependent_settings': {
-        'include_dirs': [
-          '.',
-        ],
-      },
-      'conditions': [
-        ['OS=="win"', {
-          'product_name': 'libbzip2',
-        }, {  # else: OS!="win"
-          'product_name': 'bz2',
-        }],
-      ],
-    },
+    }, {
+      'targets': [
+        {
+          'target_name': 'bzip2',
+          'type': '<(library)',

[Evan Martin, 2009/08/05 22:54:49]

This might need to be type "none", so that dependent libraries don't attempt to
add -lbzip2 (the target name) to the link line.  Grep the other gyp files for
other examples.

+
+          'defines': [
+            'USE_SYSTEM_LIBBZ2',
+          ],
+
+          # There aren't any pkg-config files for libbz2
+          'link_settings': {
+            'libraries': [
+              '-lbz2',
+            ],
+          },
+        },
+      ]
+    }],
   ],
 }