hg: jdk8u/jdk8u: 8269468: JDK-8269388 breaks the build on older GCCs

[gnu.andrew at redhat.com]

Changeset: 26920b304bf9
Author:    andrew
Date:      2021-06-28 19:46 +0100
URL:       https://hg.openjdk.java.net/jdk8u/jdk8u/rev/26920b304bf9

8269468: JDK-8269388 breaks the build on older GCCs
Summary: Only set -Wno-error=format-overflow when -Wformat-overflow is supported
Reviewed-by: aph, sgehwolf

! common/autoconf/flags.m4
! common/autoconf/generated-configure.sh
! common/autoconf/hotspot-spec.gmk.in