Enable shared library build

gyp/common_conditions.gypi

Index: gyp/common_conditions.gypi
===================================================================
--- gyp/common_conditions.gypi	(revision 9315)
+++ gyp/common_conditions.gypi	(working copy)
@@ -130,6 +130,17 @@
               '-Werror',
             ],
           }],
+          [ 'skia_shared_lib', {
+            'cflags': [
+              '-fPIC',
+            ],
+            'defines': [
+              'GR_DLL=1',
+              'GR_IMPLEMENTATION=1',
+              'SKIA_DLL',
+              'SKIA_IMPLEMENTATION=1',
+            ],
+          }],
           [ 'skia_arch_width == 64', {
             'cflags': [
               '-m64',
@@ -193,6 +204,19 @@
               ],
             },
           }],
+          [ 'skia_shared_lib', {
+            'xcode_settings': {
+              'OTHER_CPLUSPLUSFLAGS': [
+                '-fpic',
+              ],
+            },
+            'defines': [
+              'GR_DLL=1',
+              'GR_IMPLEMENTATION=1',
+              'SKIA_DLL',
+              'SKIA_IMPLEMENTATION=1',
+            ],
+          }],
         ],
         'configurations': {
           'Debug': {
@@ -259,6 +283,19 @@
               ],
             },
           }],
+          [ 'skia_shared_lib', {
+            'xcode_settings': {
+              'OTHER_CPLUSPLUSFLAGS': [
+                '-fpic',
+              ],
+            },
+            'defines': [
+              'GR_DLL=1',
+              'GR_IMPLEMENTATION=1',
+              'SKIA_DLL',
+              'SKIA_IMPLEMENTATION=1',
+            ],
+          }],
         ],
         'configurations': {
           'Debug': {
@@ -326,6 +363,17 @@
           [ 'skia_profile_enabled == 1', {
             'cflags': ['-g', '-fno-omit-frame-pointer', '-marm', '-mapcs'],
           }],
+          [ 'skia_shared_lib', {
+            'cflags': [
+              '-fPIC',
+            ],
+            'defines': [
+              'GR_DLL=1',
+              'GR_IMPLEMENTATION=1',
+              'SKIA_DLL',
+              'SKIA_IMPLEMENTATION=1',
+            ],
+          }],
           [ 'skia_arch_type == "arm" and arm_thumb == 1', {
             'cflags': [
               '-mthumb',