hg: jdk/sandbox: 8234809: set relro in linker flags when building with gcc

[chris.hegarty at oracle.com]

Changeset: a2441ac23eeb
Author:    mbaesken
Date:      2019-11-26 13:55 +0100
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/a2441ac23eeb

8234809: set relro in linker flags when building with gcc
Reviewed-by: erikj, fweimer

! make/autoconf/flags-ldflags.m4