[clang] [llvm] [ARM] musttail fixes (PR #102896)

[Eli Friedman via cfe-commits]

https://github.com/efriedma-quic commented:

Please also add a testcase for something like:
```
struct Large { int x[60]; };
void f(long long a, long long b, Large c, Large d);
void g(long long a, long long b, Large c, Large d) {
  [[clang::musttail]] return f(a,b,d,c);
}
```

https://github.com/llvm/llvm-project/pull/102896