GN: add is_official_build

... and use it to control debug symbols and SK_ALLOW_STATIC_GLOBAL_INITIALIZERS.

This will most directly have the effect of disabling GLProgramsTest and a bunch
of similar failing Vk tests on Android.

Hopefully this makes the N7 trybot go green, keeping the N5 trybot green.  Just running the N10 for fun.

(is_official_build is how Chrome terms this sort of ReleaseForReal build.)

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2340723003

Review-Url: https://codereview.chromium.org/2340723003
diff --git a/BUILD.gn b/BUILD.gn
index f14a027..05fe350 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -85,6 +85,10 @@
       "SK_GAMMA_CONTRAST=0.0",
     ]
   }
+  if (is_official_build || is_android) {
+    # TODO(bsalomon): it'd be nice to make Android normal.
+    defines += [ "SK_ALLOW_STATIC_GLOBAL_INITIALIZERS=0" ]
+  }
 }
 
 # Any code that's linked into Skia-the-library should use this config via += skia_library_configs.