[Buildroot] [git commit branch/2021.05.x] package/ibrdtn-tools: fix build with gcc 11

[Peter Korsgaard]

commit: https://git.buildroot.net/buildroot/commit/?id=1f4fad7c587b140ee301cc28bd083a32e520aea6
branch: https://git.buildroot.net/buildroot/commit/?id=refs/heads/2021.05.x

Fixes:
 - No autobuilder failures yet

Signed-off-by: Fabrice Fontaine <fontaine.fabrice at gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni at bootlin.com>
(cherry picked from commit 278072520c76bae03916cdcd2f5d3324f4626c5f)
Signed-off-by: Peter Korsgaard <peter at korsgaard.com>
---
 package/ibrdtn-tools/ibrdtn-tools.mk | 1 +
 1 file changed, 1 insertion(+)

diff --git a/package/ibrdtn-tools/ibrdtn-tools.mk b/package/ibrdtn-tools/ibrdtn-tools.mk
index 97ec3c9e17..77dbfc1032 100644
--- a/package/ibrdtn-tools/ibrdtn-tools.mk
+++ b/package/ibrdtn-tools/ibrdtn-tools.mk
@@ -9,6 +9,7 @@ IBRDTN_TOOLS_SITE = https://www.ibr.cs.tu-bs.de/projects/ibr-dtn/releases
 IBRDTN_TOOLS_LICENSE = Apache-2.0
 IBRDTN_TOOLS_LICENSE_FILES = COPYING
 IBRDTN_TOOLS_DEPENDENCIES = ibrcommon ibrdtn host-pkgconf
+IBRDTN_TOOLS_CONF_ENV = CXXFLAGS="$(TARGET_CXXFLAGS) -std=c++11"
 
 ifeq ($(BR2_STATIC_LIBS),y)
 IBRDTN_TOOLS_CONF_ENV += LDFLAGS="$(TARGET_LDFLAGS) -pthread"