build:small fixes to arm_sdimage.

* Use the same output directory as was previously the standard.
* Add copying of uEnv and cmdline to the obj directory to allow booting from tftp.
* No longer start qemu at the end of the process.
* Use sudo if the script was called as non root user.

Change-Id: I53143b1ce6633e764d173c3eb883c2efa3e6a5b7
pax: Replace bsdtar.1 by a symlink to tar.1

Change-Id: I4b80080e9420e89525c73f03ed68717fb59c1e40
UDS: terminate canonical path string

When you provided a string with junk after the terminating nul to a
UNIX domain socket and used bind(2), the canonical path function would
not properly terminate the new string. This caused VFS to return
ENAMETOOLONG on an otherwise valid path name.

Test case is added to test56.

Change-Id: I883b6be23d9e4ea13c3cee28cbb3726343df037f
test56: unlink proper test file

Change-Id: I215f0d00b8e077930c4e93d192553eaf0d2a353f
Importing usr.bin/getopt