Test/hlsl.inf.vert tests parsing and some constant math on
infinities, including (-1.#INF * 0.0).
By IEEE 754 rules, that result is a NaN, but its sign is not significant.
The test output assumes a negative-NaN is in the generated SPIR-V.
However, the math library on some platforms (like macOS 14, a.k.a.
Sonoma) will produce a positive NaN instead.
This PR adjusts the test so it takes the absolute value of the NaN,
to ensure we the emitted SPIR-V has the NaN with a 0 for it sign bit.