Update GYP for linux Vulkan to support SDK 1.0.13

gyp/gpu.gyp

Index: gyp/gpu.gyp
diff --git a/gyp/gpu.gyp b/gyp/gpu.gyp
index f09bcd0fc6e0fbcb172fbef96228ae6fa813e065..157cbed15fd1eb41fae9121de901e2fe9d619d4f 100644
--- a/gyp/gpu.gyp
+++ b/gyp/gpu.gyp
@@ -207,6 +207,22 @@
                 'vulkan_lib_name': '-lvulkan',
               },
             }],
+            [ 'skia_os == "linux"', {
+              'variables': {
+                'vulkan_sdk_path' : '<!(echo $VULKAN_SDK)',
+              },
+              'include_dirs': [
+                '<(vulkan_sdk_path)/include',
+              ],
+              'direct_dependent_settings': {
+                'include_dirs': [
+                  '<(vulkan_sdk_path)/include',
+                ],
+              },
+              'link_settings': {
+                'library_dirs': [ '<(vulkan_sdk_path)/lib', ],
+              },
+            }],
           ],
           'dependencies': [
             'shaderc.gyp:shaderc_combined',