gn2bp: Add is_debug and is_official_build to args.gn

args.gn generated by `cr_cronet.py gn --release` has is_debug=false and
is_official_build=true.
But current args.gn used to generate desc jsons were missing them.

Test: ./gen_desc_json.sh
Bug: 265913942
Change-Id: Ide83e770ade8574fe3d3ffe04f5481b8fde4140a
diff --git a/tools/gn2bp/gen_desc_json.sh b/tools/gn2bp/gen_desc_json.sh
index 6d1a4f2..1f60eb9 100755
--- a/tools/gn2bp/gen_desc_json.sh
+++ b/tools/gn2bp/gen_desc_json.sh
@@ -54,6 +54,8 @@
     "treat_warnings_as_errors = false"
     "enable_base_tracing = false"
     "is_cronet_build = true"
+    "is_debug = false"
+    "is_official_build = true"
   )
   gn_args+=("target_cpu = \"${1}\"")