python used in buildman doesn't need to be placed in
/usr/bin/python, So use env to ensure that the interpreter
will pick the python from environment.
Usefull with several versions of python's installed on system.
Signed-off-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>
Acked-by: Simon Glass <sjg@chromium.org>