package/hiawatha: fix build when c++ support is disabled

Fixes
http://autobuild.buildroot.net/results/c04/c04ff29b83c020573add597c355c57a6d9c9761d/

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/hiawatha/0001-cmake-allow-build-without-c.patch

@@ -0,0 +1,34 @@
+From 784e46afd7530f3010726ba73cc1a81059eae8bf Mon Sep 17 00:00:00 2001
+From: Bernd Kuhls <bernd.kuhls@t-online.de>
+Date: Mon, 5 Jun 2017 13:26:18 +0200
+Subject: [PATCH] cmake: allow build without c++
+
+By default cmake also searches for a c++ compiler:
+https://cmake.org/cmake/help/v3.7/command/project.html
+"By default C and CXX are enabled if no language options are given."
+
+This patch restricts the compiler to C to fix a build error detected
+by the buildroot autobuilders:
+http://autobuild.buildroot.net/results/c04/c04ff29b83c020573add597c355c57a6d9c9761d/build-end.log
+
+Patch sent upstream: https://github.com/hsleisink/hiawatha/pull/30
+
+Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
+---
+ CMakeLists.txt | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index 4f28d76..e8051fc 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -1,5 +1,5 @@
+ cmake_minimum_required(VERSION 3.0)
+-project(Hiawatha VERSION 10.6)
++project(Hiawatha VERSION 10.6 LANGUAGES C)
+ 
+ # Compiler
+ set(CMAKE_C_FLAGS "-O2 -Wall -Wextra ${CMAKE_C_FLAGS}")
+-- 
+2.11.0
+