Fix problem with missing target.txt for x86_64 build

Fix problem with missing target.txt for x86_64 build

Commit fixes patch apparent in the x86_64 build. In
style_format.py we are trying to obtain the target from the
target.txt. For the x86_64 target.txt it is not created to
use statically linked nodejs.

Now in the style_format.py we will assume default target as
tizen. If we will found the target.txt file, then we will
read the target from it.

Change-Id: I48a99c3368e71b0c35f0846cb0f74ad2a11fee67
Signed-off-by: Aleksander Świniarski <a.swiniarski@samsung.com>