Override product_extension instead of product_version to set SONAME for Linux shared library

BUG=v8:1786

Review URL: http://codereview.chromium.org/8462006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9884 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

tools/gyp/v8.gyp

@@ -72,11 +72,7 @@
                   },
                 }],
                 ['soname_version!=""', {
-                  # Ideally, we'd like to specify the full filename for the
-                  # library and set it to "libv8.so.<(soname_version)",
-                  # but currently the best we can do is use 'product_name' and
-                  # get "libv8-<(soname_version).so".
-                  'product_name': 'v8-<(soname_version)',
+                  'product_extension': 'so.<(soname_version)',
                 }],
               ],
             },