hg: jdk/sandbox: Fix compiler flags for all compilers.

[magnus.ihse.bursie at oracle.com]

Changeset: 02cec376750e
Author:    ihse
Date:      2018-02-13 14:54 +0100
URL:       http://hg.openjdk.java.net/jdk/sandbox/rev/02cec376750e

Fix compiler flags for all compilers.

! make/autoconf/flags.m4
! make/hotspot/lib/CompileLibjsig.gmk
! make/lib/LibCommon.gmk