Bind-mount /run if it exists
Bind-mount /run if it exists

Ubuntu 11.10, for whatever reason, moved /dev/shm to /run/shm.  Since
/run is not mounted in the chroot, /dev/shm is a dangling symlink and
various things that require shared memory start failing.

If /run and /run/shm exist, bind-mount them in the chroot.

Because /run doesn't yet exist in the SDK tarballs, try to create it
(and /run/shm if necessary) as root if it and can't be created as a
normal user.

BUG=chromium-os:19871
TEST=Run cros_sdk, verify that /dev/shm has the expected contents

Change-Id: I61583c1c0d409c1234fa8d8930a9b64544c9a8e7
Reviewed-on: https://gerrit.chromium.org/gerrit/10222
Tested-by: Aaron Plattner <7c39395e2e801146cdbd7fb4a41282e4f38db44e@nvidia.com>
Reviewed-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Commit-Ready: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>

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