Add libraries to fix Ubuntu13 Clang build

gyp/common_conditions.gypi

Index: gyp/common_conditions.gypi
===================================================================
--- gyp/common_conditions.gypi	(revision 10793)
+++ gyp/common_conditions.gypi	(working copy)
@@ -247,12 +247,15 @@
                 '-pthread',
               ],
             },
+          }, {

[djsollen, 2013/08/19 18:02:10]

can  you comment that this is skia_os != "nacl"

[borenet, 2013/08/19 18:05:27]

Done.

+            'link_settings': {
+              'ldflags': [
+                '-lstdc++',
+                '-lm',
+              ],
+            },
           }],
           [ 'skia_os == "chromeos"', {

[bungeman-skia, 2013/08/19 18:05:32]

Since this block seems to now be empty, shout this be != and the following line
removed? I assume this now just means to not use arch_width  with chromeos.

[borenet, 2013/08/19 18:08:01]

Done.

-            'ldflags': [
-              '-lstdc++',
-              '-lm',
-            ],
           }, {
             'conditions': [
               [ 'skia_arch_width == 64 and skia_arch_type == "x86"', {