$OpenBSD: patch-CMakeLists_txt,v 1.6 2015/11/16 20:29:55 sthen Exp $

use FindBacktrace.cmake (added in cmake 3)

--- CMakeLists.txt.orig	Mon Nov 16 09:57:03 2015
+++ CMakeLists.txt	Mon Nov 16 17:00:02 2015
@@ -188,15 +188,14 @@ set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -DI2_D
 set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -DI2_DEBUG")
 
 check_function_exists(vfork HAVE_VFORK)
-check_function_exists(backtrace_symbols HAVE_BACKTRACE_SYMBOLS)
 check_function_exists(pipe2 HAVE_PIPE2)
 check_function_exists(nice HAVE_NICE)
 check_library_exists(dl dladdr "dlfcn.h" HAVE_DLADDR)
-check_library_exists(execinfo backtrace_symbols "" HAVE_LIBEXECINFO)
 check_include_file_cxx(cxxabi.h HAVE_CXXABI_H)
 
-if(HAVE_LIBEXECINFO)
-  set(HAVE_BACKTRACE_SYMBOLS TRUE)
+find_package(Backtrace)
+if(Backtrace_FOUND)
+  include_directories(${Backtrace_INCLUDE_DIRS})
 endif()
 
 if(UNIX)
