Make component=shared_library gyp build work for Linux.

tools/gyp/v8.gyp

 # Copyright 2011 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 169 matching lines @@
       'targets': [
         {
           'target_name': 'v8',
           'conditions': [
             ['v8_use_snapshot=="true"', {
               'dependencies': ['v8_snapshot'],
             },
             {
               'dependencies': ['v8_nosnapshot'],
             }],
-            ['OS=="win" and component=="shared_library"', {
+            ['component=="shared_library"', {
               'type': '<(component)',
               'sources': [
+                # Note: on non-Windows we still build this file so that gyp
+                # has some sources to link into the component.
                 '../../src/v8dll-main.cc',
               ],
-              'defines': [
-                'BUILDING_V8_SHARED'
+              'conditions': [
+                ['OS=="win"', {
+                  'defines': [
+                    'BUILDING_V8_SHARED',
+                  ],
+                  'direct_dependent_settings': {
+                    'defines': [
+                      'USING_V8_SHARED',
+                    ],
+                  },
+                }, {
+                  'defines': [
+                    'V8_SHARED',
+                  ],
+                  'direct_dependent_settings': {
+                    'defines': [
+                      'V8_SHARED',
+                    ],
+                  },
+                }],
               ],
-              'direct_dependent_settings': {
-                'defines': [
-                  'USING_V8_SHARED',
-                ],
-              },
             },
             {
               'type': 'none',
             }],
           ],
           'direct_dependent_settings': {
             'include_dirs': [
                '../../include',
             ],
           },
         },
         {
           'target_name': 'v8_snapshot',
           'type': '<(library)',
           'conditions': [
-            ['OS=="win" and component=="shared_library"', {
-              'defines': [
-                'BUILDING_V8_SHARED',
+            ['component=="shared_library"', {
+              'conditions': [
+                ['OS=="win"', {
+                  'defines': [
+                    'BUILDING_V8_SHARED',
+                  ],
+                  'direct_dependent_settings': {
+                    'defines': [
+                      'USING_V8_SHARED',
+                    ],
+                  },
+                }, {
+                  'defines': [
+                    'V8_SHARED',
+                  ],
+                  'direct_dependent_settings': {
+                    'defines': [
+                      'V8_SHARED',
+                    ],
+                  },
+                }],
               ],
             }],
           ],
           'dependencies': [
             'mksnapshot#host',
             'js2c#host',
             'v8_base',
           ],
           'include_dirs+': [
             '../../src',
@@ skipping 32 matching lines @@
             '<(SHARED_INTERMEDIATE_DIR)/experimental-libraries.cc',
             '../../src/snapshot-empty.cc',
           ],
           'conditions': [
             # The ARM assembler assumes the host is 32 bits, so force building
             # 32-bit host tools.
             ['v8_target_arch=="arm" and host_arch=="x64" and _toolset=="host"', {
               'cflags': ['-m32'],
               'ldflags': ['-m32'],
             }],
-            ['OS=="win" and component=="shared_library"', {
+            ['component=="shared_library"', {
               'defines': [
                 'BUILDING_V8_SHARED',
+                'V8_SHARED',
               ],
             }],
           ]
         },
         {
           'target_name': 'v8_base',
           'type': '<(library)',
           'toolsets': ['host', 'target'],
           'include_dirs+': [
             '../../src',
@@ skipping 402 matching lines @@
             ],
             ['OS=="win"', {
               'sources': [
                 '../../src/platform-win32.cc',
               ],
               'msvs_disabled_warnings': [4351, 4355, 4800],
               'link_settings':  {
                 'libraries': [ '-lwinmm.lib' ],
               },
             }],
-            ['OS=="win" and component=="shared_library"', {
+            ['component=="shared_library"', {
               'defines': [
-                'BUILDING_V8_SHARED'
+                'BUILDING_V8_SHARED',
+                'V8_SHARED',
               ],
             }],
           ],
         },
         {
           'target_name': 'js2c',
           'type': 'none',
           'toolsets': ['host'],
           'variables': {
             'library_files': [
@@ skipping 109 matching lines @@
           'target_name': 'v8_shell',
           'type': 'none',
           'dependencies': [
             'v8'
           ],
         },
       ],
     }],
   ],
 }