Disable EAP-GTC on Android.

The EAP-GTC plugin does not compile due to its dependency on PAM.

Android.mk.in

@@ -5,7 +5,7 @@ include $(CLEAR_VARS)
 # also these plugins are loaded by default (if not changed in strongswan.conf)
 strongswan_PLUGINS := openssl fips-prf random pubkey pkcs1 \
 	pem xcbc hmac kernel-netlink socket-default android \
-	eap-identity eap-mschapv2 eap-gtc eap-md5
+	eap-identity eap-mschapv2 eap-md5
 
 # helper macros to only add source files for plugins included in the list above
 # source files are relative to the android.mk that called the macro