Index: erts/lib_src/Makefile.in
--- erts/lib_src/Makefile.in.orig
+++ erts/lib_src/Makefile.in
@@ -47,7 +47,7 @@ ERLANG_OSTYPE=@ERLANG_OSTYPE@
 OMIT_FP=false
 empty:=
 space:=$(empty) $(empty)
-CFLAGS:=$(subst $(space)-O2$(space), -O3 , @CFLAGS@)
+CFLAGS:=@CFLAGS@
 LDFLAGS=@LDFLAGS@
 
 ifeq ($(TYPE),debug)
