ibrdtnd: fix compilation with GCC11

throw() is not compatible with C++17.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

net/ibrdtnd/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=ibrdtnd
 PKG_VERSION:=1.0.1
-PKG_RELEASE:=6
+PKG_RELEASE:=7
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=http://www.ibr.cs.tu-bs.de/projects/ibr-dtn/releases
@@ -46,6 +46,8 @@ CONFIGURE_ARGS += \
 	--without-vmime \
 	--disable-libdaemon
 
+TARGET_CXXFLAGS += -std=c++11
+
 define Package/ibrdtnd/install
 	$(INSTALL_DIR) $(1)/usr/sbin/
 	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/sbin/dtnd $(1)/usr/sbin/