Enable GCM, too. I'm not clear on what it is but default_options.h says

it should be enabled for compatibility if you can spare 6kB of executable
size.  Anyways, it's new.

dropbear/localoptions.h

@@ -302,3 +302,4 @@ be overridden at runtime with -I. 0 disables idle timeouts */
 
 #define BUNDLED_LIBTOM 1
 #define DROPBEAR_ED25519 1
+#define DROPBEAR_ENABLE_GCM_MODE 1

jni/Android.mk

@@ -30,6 +30,7 @@ DROPBEAR_SRCS := $(DROPBEAR_PATH)/atomicio.c \
 	$(DROPBEAR_PATH)/ecdsa.c \
 	$(DROPBEAR_PATH)/ed25519.c \
 	$(DROPBEAR_PATH)/fake-rfc2553.c \
+	$(DROPBEAR_PATH)/gcm.c \
 	$(DROPBEAR_PATH)/gendss.c \
 	$(DROPBEAR_PATH)/gened25519.c \
 	$(DROPBEAR_PATH)/genrsa.c \