[ROCm] Guard placement new/delete to fix build on ROCm 7.12+

ROCm 7.12 (clang 22) provides __device__ placement new/delete
via cuda_wrappers/new, causing redefinition errors. Guard with
__CLANG_CUDA_WRAPPERS_NEW so the manual definitions are only
compiled on older ROCm versions that lack them.

Author: Geramy

mlx/backend/rocm/sort.hip

@@ -10,12 +10,15 @@
 
 // Workaround: rocprim headers use placement new in __device__ code,
 // which requires __device__ overloads of operator new/delete.
+// ROCm 7.12+ (clang 22+) already provides these via cuda_wrappers/new.
 #ifdef __HIP_DEVICE_COMPILE__
+#ifndef __CLANG_CUDA_WRAPPERS_NEW
 __device__ inline void* operator new(size_t, void* p) noexcept { return p; }
 __device__ inline void* operator new[](size_t, void* p) noexcept { return p; }
 __device__ inline void operator delete(void*, void*) noexcept {}
 __device__ inline void operator delete[](void*, void*) noexcept {}
 #endif
+#endif
 
 #include <rocprim/rocprim.hpp>
 #include <cassert>