Set build vars for Vulkan backend on Fuchsia.

BUG=skia:

Change-Id: I355209a170ad8930a59cf91d584f40de82f51b92
Reviewed-on: https://skia-review.googlesource.com/13563
Reviewed-by: Forrest Reiling <freiling@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 64944b1..f700ac6 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -37,7 +37,7 @@
   skia_enable_tools = is_skia_dev_build
   skia_enable_vulkan_debug_layers = is_skia_dev_build && is_debug
   skia_vulkan_sdk = getenv("VULKAN_SDK")
-  skia_link_with_vulkan = true
+  skia_link_with_vulkan = !is_fuchsia
 }
 declare_args() {
   skia_use_dng_sdk = !is_fuchsia && skia_use_libjpeg_turbo && skia_use_zlib
@@ -140,7 +140,7 @@
   libs = []
   lib_dirs = []
   if (skia_use_vulkan) {
-    if (skia_vulkan_sdk != "" && !is_android) {
+    if (skia_vulkan_sdk != "" && !is_android && !is_fuchsia) {
       if (is_win) {
         lib_dirs += [
           "$skia_vulkan_sdk/Bin",