Fix Chrome iOS no GPU build and block includes from src/gpu on our NoGpu bot.

Change-Id: I934f0d6096a6eb0305e24f06dfb6c49299a195a9
Reviewed-on: https://skia-review.googlesource.com/8919
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index c162842..af188f8 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -99,7 +99,6 @@
     "src/effects",
     "src/effects/gradients",
     "src/fonts",
-    "src/gpu",
     "src/image",
     "src/images",
     "src/lazy",
@@ -148,6 +147,9 @@
       libs += [ "vulkan" ]
     }
   }
+  if (skia_enable_gpu) {
+    include_dirs += [ "src/gpu" ]
+  }
   if (skia_use_angle) {
     defines += [ "SK_ANGLE" ]
   }