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

[via cfe-commits]

kiran-isaac wrote:

> 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);
> }
> ```

added this testcase (compiled to ir), it works with my patch and does not without

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