--- configure.orig	2021-10-14 09:28:15 UTC
+++ configure
@@ -6984,7 +6984,7 @@ fi
 	echo "* (otherwise, a default of CFLAGS=-O3 will be used)    *"
 	echo "********************************************************"
 	echo ""
-        CFLAGS="-O3"
+        CFLAGS="$ac_cv_env_CFLAGS_value"
   fi
 
    { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether C compiler accepts $CFLAGS" >&5