Fix PNaCl install directory.
Fix PNaCl install directory.

This was breaking all the builtbots as --clean was removing
the /usr folder rather than the /usr/local, which was removing
all the PNaCl system headers.

R=binji@chromium.org, binji

Review URL: https://codereview.chromium.org/312603002

git-svn-id: 84b3587ce119b778414dcb50e18b7479aacf4f1d@1297 7dad1e8b-422e-d2af-fbf5-8013b78bd812

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