GR_TEST_UTILS fixes

Fixes build of Skia lib when GR_TEST_UTILS=0

Makes GR_TEST_UTILS=0 for official builds

Makes "Mini" builder bot exercise building GPU with is_official_build=true

Bug: skia:6786
Change-Id: I6186683a3a216d2e779645bd9e8276a66bcff4d5
Reviewed-on: https://skia-review.googlesource.com/21524
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index f5d1dd6..9b2859c 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -184,6 +184,9 @@
   if (skia_enable_discrete_gpu) {
     defines += [ "SK_ENABLE_DISCRETE_GPU" ]
   }
+  if (!is_official_build) {
+    defines += [ "GR_TEST_UTILS=1" ]
+  }
 }
 
 # Any code that's linked into Skia-the-library should use this config via += skia_library_configs.