security_Minijail0: unbreak test-chroot

There were two problems:
1) If we don't bind-mount /usr/local into the chroot, we can't run the test
script;
2) There's no touch in the chroot, so use echo instead.

Change-Id: Ie7291ea1503ded95aeb4c346636b4a51db7569ca
Reviewed-on: https://gerrit.chromium.org/gerrit/13091
Reviewed-by: Will Drewry <wad@chromium.org>
Commit-Ready: Elly Jones <ellyjones@chromium.org>
Tested-by: Elly Jones <ellyjones@chromium.org>
2 files changed