[clang] [AArch64][PAC] Emit `!dbg` locations in `*_vfpthunk_` functions (PR #179688)

[Anatoly Trosinenko via cfe-commits]

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atrosinenko wrote:

Frankly speaking, I'm not familiar with the particular specifics of pointers to member functions. Nonetheless, both the issue itself and a typical solution (which can be observed in other similar places) seem to be rather clear. The [documentation](https://github.com/llvm/llvm-project/blob/ce6dd9ca1912c63ad947523eee173ea78121cceb/clang/lib/CodeGen/CGDebugInfo.h#L942) of `ApplyDebugLocation::CreateArtificial` explicitly mentions this: "Artificial locations are useful when emitting compiler-generated helper functions that have no source location associated with them".

`ApplyDebugLocation::CreateArtificial` is called by other similar functions: [1](https://github.com/llvm/llvm-project/blob/ce6dd9ca1912c63ad947523eee173ea78121cceb/clang/lib/CodeGen/CGBlocks.cpp#L1963), [2](https://github.com/llvm/llvm-project/blob/ce6dd9ca1912c63ad947523eee173ea78121cceb/clang/lib/CodeGen/CGBuiltin.cpp#L2187), [3](https://github.com/llvm/llvm-project/blob/ce6dd9ca1912c63ad947523eee173ea78121cceb/clang/lib/CodeGen/CGDeclCXX.cpp#L257) and many others.

For this test file, I simply used the same name as in the original #99576 that introduced this feature and corresponding test file under `cland/test/CodeGenCXX`.

https://github.com/llvm/llvm-project/pull/179688