[clang] [Sema] Substitute parameter packs when deduced from function arguments (PR #79371)

[Gábor Spaits via cfe-commits]

spaits wrote:

I did some more digging. I saw that the test in the CI fails with permission errors.

```
| No symbol table is loaded.  Use the "file" command.
| warning: opening /proc/PID/mem file for lwp 4103309.4103309 failed: Permission denied (13)
| Traceback (most recent call last):
|   File "/var/lib/buildkite-agent/builds/linux-56-59b8f5d88-h5ngp-1/llvm-project/clang-ci/libcxx/test/libcxx/gdb/gdb_pretty_printer_test.py", line 123, in <module>
|     gdb.execute("run")
| gdb.error: Warning:
| Cannot insert breakpoint 1.
| Cannot access memory at address 0x55555555637c
```

I thought that maybe the problem is that, the program to be debugged by `dbg` does not compile with the compiler that includes my changes. I decided to just compile the test file with my modified compiler. I copied the test file. Removed one include that is only needed for manual debugging and recreated the command used in the CI as much as I could. The command looks like this now:
```
/home/spaits/repo/llvm-project/build/bin/clang++ -pthread --target=x86_64-unknown-linux-gnu /home/spaits/cpp/deb.cpp -o /home/spaits/cpp/deb.out -std=c++26 -Werror -Wall -Wctad-maybe-unsupported -Wextra -Wshadow -Wundef -Wunused-template -Wno-unused-command-line-argument -Wno-attributes -Wno-pessimizing-move -Wno-noexcept-type -Wno-atomic-alignment -Wno-reserved-module-identifier -Wdeprecated-copy -Wdeprecated-copy-dtor -Wno-user-defined-literals -Wno-tautological-compare -Wsign-compare -Wunused-variable -Wunused-parameter -Wunreachable-code -Wno-unused-local-typedef -Wno-local-type-template-args -Wno-c++11-extensions -Wno-unknown-pragmas -Wno-pass-failed -Wno-mismatched-new-delete -Wno-redundant-move -Wno-self-move -D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -D_LIBCPP_ENABLE_EXPERIMENTAL -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_NONE -Werror=thread-safety -Wuser-defined-warnings -g   -lc++ -latomic
0 spaits at work-laptop:~/cpp$ 
```
Because of the GCC 13+ prereq. I did not build libc++ for my self, but used the one available on my machine.
This way the file has compiled successfully.

I will still try to run the tests myself.

Until that if you have any idea what should I, do what wen possibly wrong pleas share that with me.

Thanks.

https://github.com/llvm/llvm-project/pull/79371