hg: macosx-port/macosx-port/jdk: Allow ARCH=amd64/i586 to be set from the environment to override 'universal'

[astrange at apple.com]

Changeset: b8f9a55fad8b
Author:    astrange
Date:      2011-06-27 13:16 -0700
URL:       http://hg.openjdk.java.net/macosx-port/macosx-port/jdk/rev/b8f9a55fad8b

Allow ARCH=amd64/i586 to be set from the environment to override 'universal'

! make/common/shared/Platform.gmk