LLVM takes liberties with NaN float constants, which can arise in integer
constant values.

Bug b/140294254

Test: dEQP-VK.spirv_assembly.type.vec3.u32.constant_composite_frag
Change-Id: Ibfff77b9e0bacf81756bb50801615369dfc51ab6
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/35728
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>