gn2bp: disable rtti in protobufs

libprotobuf is compiled with -fno-rtti, so disable it for all protobufs.

Test: //components/cronet/android:cronet
Change-Id: Ied846201a5cff765b464b846b38f4c2ae2ddda5d
diff --git a/tools/gn2bp/Android.bp.swp b/tools/gn2bp/Android.bp.swp
index 33bfbcd..fdb7324 100644
--- a/tools/gn2bp/Android.bp.swp
+++ b/tools/gn2bp/Android.bp.swp
@@ -2404,6 +2404,7 @@
 cc_defaults {
     name: "cronet_aml_defaults",
     cflags: [
+        "-DGOOGLE_PROTOBUF_NO_RTTI",
         "-O2",
         "-Wno-deprecated-non-prototype",
         "-Wno-error=return-type",