hg: build-infra/jdk9: Make compare script ln silent in case of pre-existing symlink.

[magnus.ihse.bursie at oracle.com]

Changeset: 89e22174b542
Author:    ihse
Date:      2014-09-02 14:54 +0200
URL:       http://hg.openjdk.java.net/build-infra/jdk9/rev/89e22174b542

Make compare script ln silent in case of pre-existing symlink.

! common/bin/compare.sh