__spirv_GenericCastToPtrExplicit_To* builtin, used in sycl header, has wrong mangled name for spir64 target

[wenju-he]

Describe the bug

When test sycl_cts/address_space_core is compiled with spir64 target, __spirv_GenericCastToPtrExplicit_ToPrivate builtin in device code is mangled as

declare dso_local spir_func noundef ptr @_Z42__spirv_GenericCastToPtrExplicit_ToPrivatePvi(ptr addrspace(4) noundef, i32 noundef) 

However, the correct mangled name should be _Z42__spirv_GenericCastToPtrExplicit_ToPrivatePU3AS4vi
This is causing name mismatch if a variant of libclc libspirv that also use 4 as generic addrspace is linked to the device code via -mlink-builtin-bitcode option before llvm-link step.
Please advise if this issue should be fixed in SYCL FE.

-fsycl-targets=amdgcn-amd-amdhsa and -fsycl-targets=nvptx64-nvidia-cuda don't have this issue because their flat address space is 0.

To reproduce

1. checkout test code https://github.com/KhronosGroup/SYCL-CTS/blob/main/tests/address_space/address_space_core.cpp
2. compile the test and dump device code before llvm-link step.

clang++ -fsycl ./tests/address_space/address_space_core.cpp -I./vendor/Catch2/src/catch2/.. -I./build/vendor/Catch2/generated-includes

Environment

• OS: Linux
• Target device and vendor: spir64
• clang++ --version: clang version 20.0.0git (https://github.com/intel/llvm.git 2fcddee)

Additional context

No response