[libclc] libclc: clspv: add missing clc_isnan.cl dependency (PR #124614)

[Romaric Jodin via cfe-commits]

rjodinchr wrote:

@frasercrmck , I cannot merge it myself, could you do it please?

> Should spirv/SOURCES and spirv64/SOURCES receive the same thing?

I'm not sure, I would guess yes, but without testing it, it's hard to be 100% sure.

https://github.com/llvm/llvm-project/pull/124614