GN: Mark dl sourceset as non-chromium code to silence compiler warnings

Warnings show when target_cpu="arm64"

BUG=568883
NOTRY=true
NOPRESUBMIT=true
R=rtoy@google.com

Review URL: https://codereview.webrtc.org/1520893002 .
diff --git a/dl/BUILD.gn b/dl/BUILD.gn
index 5459f48..c5b6d36 100644
--- a/dl/BUILD.gn
+++ b/dl/BUILD.gn
@@ -40,6 +40,8 @@
 # GYP: third_party/openmax_dl/dl/dl.gyp:openmax_dl
 source_set("dl") {
   public_configs = [ ":dl_config" ]
+  configs -= [ "//build/config/compiler:chromium_code" ]
+  configs += [ "//build/config/compiler:no_chromium_code" ]
   sources = [
     "api/omxtypes.h",
     "sp/api/omxSP.h",