hg: build-infra/jdk8: Only show the annoying performance hints about ccache once (I *know* I don't

[magnus.ihse.bursie at oracle.com]

Changeset: d7afc59d90dd
Author:    ihse
Date:      2012-06-11 15:29 +0200
URL:       http://hg.openjdk.java.net/build-infra/jdk8/rev/d7afc59d90dd

Only show the annoying performance hints about ccache once (I *know* I don't
have an up-to-date ccache for my system...)

! common/autoconf/configure.ac
! common/autoconf/generated-configure.sh