Only generate fake root signature for ancient compilers.

In the case where we actually have a non-zero compiler version, the metadata
provided will have the proper information about root(). The bug here is that
sometimes a graphics root() function will end up looking like a compute
root() function (specified with attribute kernel).

Change-Id: I49eb1d555a41552e1345badd5c2001807feeea9b
1 file changed