Add support for cross-compilation

Add support for cross-compilation

crosscompile is useful for development purposes. I do not intend to replace
gbs with this, just to help developers (including myself) doing their job quicker.
The idea is that once you built with gbs you can use it's build root together
with the tizen sdk to crosscompile for mobile.

Co-authored by Balazs Kelemen and Tomasz Olszak.

Bug: http://107.108.218.239/bugzilla/show_bug.cgi?id=6110
Reviewed by: Balazs Kelemen, Piotr Tworek, SeungSeop Park
Reviewed by: Antonio Gomes, SeungSeop Park

Change-Id: Iff75f7e0917aa7141fb075d46a3734c94cbf5a8b
Signed-off-by: Balazs Kelemen <b.kelemen@samsung.com>
Signed-off-by: Tomasz Olszak <t.olszak@samsung.com>
Signed-off-by: Piotr Tworek <p.tworek@samsung.com>