build: Fix python3 printf syntax

Using as default on build host Python3.4 environment,
the build of Zephyr terminates with complain.

File "<string>", line 1
      import os.path; print os.path.relpath(...)
                             ^
SyntaxError: invalid syntax

Change-Id: I99abf647ffc68d4e8a0b3d6c74a5362435670aa4
Signed-off-by: Arkadiusz Lichwa <arkadiusz.lichwa@tieto.com>
1 file changed