Add libraries to fix Ubuntu13 Clang build

R=bungeman@google.com, djsollen@google.com

Review URL: https://codereview.chromium.org/23281003

git-svn-id: http://skia.googlecode.com/svn/trunk@10796 2bbb7eff-a529-9590-31e7-b0007b416f81

gyp/common_conditions.gypi

@@ -247,13 +247,15 @@
                 '-pthread',
               ],
             },
+          }, { # skia_os != "nacl"
+            'link_settings': {
+              'ldflags': [
+                '-lstdc++',
+                '-lm',
+              ],
+            },
           }],
-          [ 'skia_os == "chromeos"', {
-            'ldflags': [
-              '-lstdc++',
-              '-lm',
-            ],
-          }, {
+          [ 'skia_os != "chromeos"', {
             'conditions': [
               [ 'skia_arch_width == 64 and skia_arch_type == "x86"', {
                 'cflags': [