[libclc] [libclc] Implement integer __clc_abs using __builtin_elementwise_abs (PR #164957)

[Wenju He via cfe-commits]

================
@@ -6,7 +6,14 @@
 //
 //===----------------------------------------------------------------------===//
 
+#ifdef __CLC_GEN_S
----------------
wenju-he wrote:

> > Does this define exist? I remember it downstream but haven't seen it upstream.
> 
> You're right, thanks. I'll add it to upstream.

done. llvm build is broken if __CLC_GEN_S is not defined.

LLVM IR change to amdgcn--amdhsa.bc:
<img width="643" height="199" alt="image" src="https://github.com/user-attachments/assets/ebcf4a40-ae41-4e05-adde-fb71fab88faa" />


https://github.com/llvm/llvm-project/pull/164957