default to O3 optimization

Signed-off-by: Niklas Eiling <niklas.eiling@eonerc.rwth-aachen.de>

cpu/Makefile

@@ -91,7 +91,7 @@ ifdef WITH_DEBUG
 # use ASAN_OPTIONS=protect_shadow_gap=0  LSAN_OPTIONS=fast_unwind_on_malloc=0 when running
 CC_FLAGS += -g -ggdb #-static-libasan -fsanitize=address -fsanitize=pointer-compare -fsanitize=pointer-subtract -fsanitize-address-use-after-scope
 else
-CC_FLAGS += -O2
+CC_FLAGS += -O3
 endif
 
 ifdef WITH_IB