generate bindings into temporary files first
Since
isl-0.18-1054-g2f9b9b4043 (detect failures in bindings generation,
Sat Jan 27 12:44:04 2018 +0100), the (partially) generated bindings
are removed if anything goes wrong during the generation.
It is safer to first generate them into temporary files and
to only move them into their intended locations when the generation
is successful.
This also ensures that even during the generation,
those files do not contain partially generated bindings.
Signed-off-by: Sven Verdoolaege <sven.verdoolaege@gmail.com>