gmp: Declare dependency on DRBG to generate private keys

src/libstrongswan/plugins/gmp/gmp_plugin.c

@@ -76,6 +76,7 @@ METHOD(plugin_t, get_features, int,
 		PLUGIN_REGISTER(PRIVKEY_GEN, gmp_rsa_private_key_gen, FALSE),
 			PLUGIN_PROVIDE(PRIVKEY_GEN, KEY_RSA),
 				PLUGIN_DEPENDS(RNG, RNG_TRUE),
+				PLUGIN_DEPENDS(DRBG, DRBG_HMAC_SHA512),
 		PLUGIN_REGISTER(PUBKEY, gmp_rsa_public_key_load, TRUE),
 			PLUGIN_PROVIDE(PUBKEY, KEY_RSA),
 		/* signature schemes, private */