devtool: sdk-install: add option to allow building from source

devtool: sdk-install: add option to allow building from source

By default the sdk-install subcommand expects to restore the requested
items from sstate and fails if it can't. If the user is OK with building
from source, add a -s/--allow-build option to allow them to do that. In
the process, ensure we show the status output while we're installing.

Also add the missing header to the top of the file.

(From OE-Core rev: a86b426cdd465ec5cb08bb5fa7729e4e673d94bb)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>