Fix issue with unused variable under some guarded conditions
Fix issue with unused variable under some guarded conditions

Guarded code causing an unused variable definition error. Fix by adding the same
guard to the def of the variable as for the use.

GPUOpen-Drivers/llpc,googlestadia/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc,googlestadia/llpc,googlestadia/llpc,googlestadia/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc,googlestadia/llpc