add -Wno-error=attributes for G3 Android builds

This warning is triggering spuriously on 32-bit Android opt builds.

This CL turns it off for {32,64}x{fastbuild,opt}, but I don't mind.
We can rely on our local builds' much more up to date toolchains.

Change-Id: I5210e87f540a1a425fc0abd07bb3c3986f0f78b0
Reviewed-on: https://skia-review.googlesource.com/15541
Reviewed-by: Ben Wagner <benjaminwagner@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

public.bzl

@@ -610,7 +610,11 @@ COPTS_UNIX = [
     "-Wno-deprecated-declarations",  # Internal use of deprecated methods. :(
 ]
 
-COPTS_ANDROID = ["-mfpu=neon"]
+COPTS_ANDROID = [
+    "-mfpu=neon",
+    "-Wno-error=attributes",  # 'GrResourceCache' declared with greater visibility than the
+                              # type of its field 'GrResourceCache::fPurgeableQueue'... bogus.
+]
 
 COPTS_IOS = []