glsl_to_tgsi: fix the value of gl_FrontFacing with native integers

We must convert it to boolean from the DX9 float encoding that Gallium
specifies.

Later, we should probably define that FACE should be 0 or ~0 if native
integers are supported.

Cc: 10.2 10.3 <mesa-stable@lists.freedesktop.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
1 file changed