Fix to bazel build file to exclude vulkan files

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1723593002

Review URL: https://codereview.chromium.org/1723593002
diff --git a/public.bzl b/public.bzl
index a8913fc..77caaf1 100644
--- a/public.bzl
+++ b/public.bzl
@@ -114,6 +114,9 @@
         "src/xml/SkBML_Verbs.h",
         "src/xml/SkBML_XMLParser.cpp",
         "src/xml/SkXMLPullParser.cpp",
+
+        # Currently exclude all vulkan specific files
+        "src/gpu/vk/*",
     ],
 )