Fix bash to emit an error when nacl_spawn/waitpid return an error.
Fix bash to emit an error when nacl_spawn/waitpid return an error.

This allows these operations to work:

$ bash -c 'exit 123'
$ echo $?
123

$ true
$ echo $?
0

$ false
$ echo $?
1

$ foo
foo: command not found
$ echo $?
127

BUG=None
TEST=None
R=channingh@google.com, sbc@chromium.org

Review URL: https://codereview.chromium.org/337623002

git-svn-id: 84b3587ce119b778414dcb50e18b7479aacf4f1d@1321 7dad1e8b-422e-d2af-fbf5-8013b78bd812

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