$OpenBSD$

Index: cmake/CompilerOptimizations.cmake
--- cmake/CompilerOptimizations.cmake.orig
+++ cmake/CompilerOptimizations.cmake
@@ -12,10 +12,10 @@ endif()
 check_c_compiler_flag(-ffast-math HAS_FAST_MATH)
 check_cxx_compiler_flag(-ffast-math HAS_CXX_FAST_MATH)
 if (HAS_FAST_MATH AND NOT MINGW)
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -ffast-math")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -ffast-math -lm")
 endif()
 if (HAS_CXX_FAST_MATH AND NOT MINGW)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -ffast-math")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -ffast-math -lm")
 endif()
 
 
