hg: macosx-port/macosx-port/jdk: Handle non-zero return value from grep when it finds no results.

[swingler at apple.com]

Changeset: 3e3d84f27c68
Author:    swingler at apple.com
Date:      2011-03-08 12:51 -0800
URL:       http://hg.openjdk.java.net/macosx-port/macosx-port/jdk/rev/3e3d84f27c68

Handle non-zero return value from grep when it finds no results.

! make/common/shared/Defs-macosx.gmk