Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt.orig
+++ CMakeLists.txt
@@ -22,6 +22,8 @@
 # CMake setup
 #
 
+INCLUDE(CMakePushCheckState)
+
 cmake_minimum_required(VERSION 2.6 FATAL_ERROR)
 if(COMMAND cmake_policy)
     cmake_policy(SET CMP0003 NEW)
@@ -198,6 +200,8 @@ if(UNIX)
         ALLEGRO_USE_CONSTRUCTOR)
 
     find_library(RT_LIBRARY rt)
+    cmake_push_check_state()
+    set(CMAKE_REQUIRED_LIBRARIES ${RT_LIBRARY})
     check_c_source_compiles("
         #include <time.h>
         int main(void) {
@@ -207,6 +211,7 @@ if(UNIX)
         }"
         ALLEGRO_HAVE_POSIX_MONOTONIC_CLOCK
         )
+    cmake_pop_check_state()
 
     if(MAGIC_MAIN)
         set(ALLEGRO_WITH_MAGIC_MAIN 1)