The patch below comes from upstream and has been slightly adjusted to apply
on the tarball we build.

From 1b663ceffe51008af7ae9749e5b7999b2f7d6698 Mon Sep 17 00:00:00 2001
From: Bernhard Miklautz <bernhard.miklautz@shacknet.at>
Date: Fri, 12 Dec 2014 18:26:45 +0100
Subject: [PATCH] build: cmake 3.1 compatibility

* fix problem with REMOVE_DUPLICATES on undefined lists
* since 3.1 file(GLOB FILEPATHS RELATIVE .. returns single / instead of // as
  previously - necessary adoptions for regex and matches done. Should
	work with all cmake versions.

Tested with 3.1.0-rc3
--- channels/CMakeLists.txt
+++ channels/CMakeLists.txt
@@ -202,8 +202,8 @@ set(FILENAME "ChannelOptions.cmake")
 file(GLOB FILEPATHS RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} "*/${FILENAME}")
 
 foreach(FILEPATH ${FILEPATHS})
-	if(${FILEPATH} MATCHES "^([^/]*)//${FILENAME}")
-		string(REGEX REPLACE "^([^/]*)//${FILENAME}" "\\1" DIR ${FILEPATH})
+	if(${FILEPATH} MATCHES "^([^/]*)/+${FILENAME}")
+		string(REGEX REPLACE "^([^/]*)/+${FILENAME}" "\\1" DIR ${FILEPATH})
 		set(CHANNEL_OPTION)
 		include(${FILEPATH})
 		if(${CHANNEL_OPTION})
--- channels/client/CMakeLists.txt
+++ channels/client/CMakeLists.txt
@@ -24,7 +24,9 @@ set(${MODULE_PREFIX}_SRCS
 	${CMAKE_CURRENT_SOURCE_DIR}/addin.c
 	${CMAKE_CURRENT_SOURCE_DIR}/addin.h)
 
+if(CHANNEL_STATIC_CLIENT_ENTRIES)
 list(REMOVE_DUPLICATES CHANNEL_STATIC_CLIENT_ENTRIES)
+endif()
 
 foreach(STATIC_ENTRY ${CHANNEL_STATIC_CLIENT_ENTRIES})
 	foreach(STATIC_MODULE ${CHANNEL_STATIC_CLIENT_MODULES})
--- third-party/CMakeLists.txt
+++ third-party/CMakeLists.txt
@@ -22,11 +22,11 @@
 file(GLOB all_valid_subdirs RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} "*/CMakeLists.txt")
 
 foreach(dir ${all_valid_subdirs})
-	if(${dir} MATCHES "^([^/]*)//CMakeLists.txt")
-		string(REGEX REPLACE "^([^/]*)//CMakeLists.txt" "\\1" dir_trimmed ${dir})
+	if(${dir} MATCHES "^([^/]*)/+CMakeLists.txt")
+		string(REGEX REPLACE "^([^/]*)/+CMakeLists.txt" "\\1" dir_trimmed ${dir})
 		message(STATUS "Adding third-party component ${dir_trimmed}")
 		add_subdirectory(${dir_trimmed})
 	endif()
 endforeach(dir)
 
-set(THIRD_PARTY_INCLUDES ${THIRD_PARTY_INCLUDES} PARENT_SCOPE)
\ No newline at end of file
+set(THIRD_PARTY_INCLUDES ${THIRD_PARTY_INCLUDES} PARENT_SCOPE)