avoid -O3

Index: CMake/setup_post_project.cmake
--- CMake/setup_post_project.cmake.orig
+++ CMake/setup_post_project.cmake
@@ -11,7 +11,7 @@ set(msvc_rwdi "/DNDEBUG /MDd /Zi /D_ITERATOR_DEBUG_LEV
 
 set(gnu_debug "-O1 -ggdb2 -fno-omit-frame-pointer")
 set(gnu_rwdi "-O2 -ggdb2 -fno-omit-frame-pointer -DNDEBUG")
-set(gnu_release "-O3 -DNDEBUG")
+set(gnu_release "-DNDEBUG")
 
 if (CMAKE_SIZEOF_VOID_P EQUAL 8)
   set(X64 1)
