[libclc] libclc: Fix missing clc prefixes on some clc files (PR #185679)

[Michał Górny via cfe-commits]

mgorny wrote:

I'm seeing test regressions after this change:

```
Start testing: Mar 11 13:54 UTC
----------------------------------------------------------
1/1 Testing: external-funcs-libclc-amdgcn-amd-amdhsa-llvm
1/1 Test: external-funcs-libclc-amdgcn-amd-amdhsa-llvm
Command: "/var/tmp/portage/llvm-core/libclc-23.0.0.9999/work/libclc/check_external_funcs.sh" "/var/tmp/portage/llvm-core/libclc-23.0.0.9999/work/libclc_build/amdgcn-amd-amdhsa-llvm/libclc.bc" "/usr/lib/llvm/23/bin"
Directory: /var/tmp/portage/llvm-core/libclc-23.0.0.9999/work/libclc
"external-funcs-libclc-amdgcn-amd-amdhsa-llvm" start time: Mar 11 13:54 UTC
Output:
----------------------------------------------------------
ERROR: 4 unresolved external functions detected in /var/tmp/portage/llvm-core/libclc-23.0.0.9999/work/libclc_build/amdgcn-amd-amdhsa-llvm/libclc.bc
declare hidden i32 @_Z15__clc_get_fencePv(ptr noundef) local_unnamed_addr #1
declare hidden ptr addrspace(1) @_Z15__clc_to_globalPv(ptr noundef) local_unnamed_addr #1
declare hidden ptr addrspace(3) @_Z14__clc_to_localPv(ptr noundef) local_unnamed_addr #1
declare hidden ptr addrspace(5) @_Z16__clc_to_privatePv(ptr noundef) local_unnamed_addr #1
<end of output>
Test time =   1.54 sec
----------------------------------------------------------
Test Failed.
"external-funcs-libclc-amdgcn-amd-amdhsa-llvm" end time: Mar 11 13:54 UTC
"external-funcs-libclc-amdgcn-amd-amdhsa-llvm" time elapsed: 00:00:01
----------------------------------------------------------

End testing: Mar 11 13:54 UTC
```

(That said, main is currently completely broken after #185788.)

https://github.com/llvm/llvm-project/pull/185679