Fix nacl-env.sh on mac (fix yaji).
Fix nacl-env.sh on mac (fix yaji).

Yaji uses golden output, errors from nacl-env.sh break this.
The recent windows fix doesn't run correctly on mac.

BUG=None
TEST=None
TBR=sbc@chromium.org

Review URL: https://codereview.chromium.org/420993002

git-svn-id: 84b3587ce119b778414dcb50e18b7479aacf4f1d@1489 7dad1e8b-422e-d2af-fbf5-8013b78bd812

yeyus/naclports,dtkav/naclports,yeyus/naclports,kuscsik/naclports,Schibum/naclports,kuscsik/naclports,yeyus/naclports,Schibum/naclports,Schibum/naclports,yeyus/naclports,kuscsik/naclports,yeyus/naclports,Schibum/naclports,dtkav/naclports,kuscsik/naclports,dtkav/naclports,Schibum/naclports,yeyus/naclports,kuscsik/naclports,dtkav/naclports,Schibum/naclports,dtkav/naclports