profile.c: implement SP/PC registers for ARM64 in get_thread_stackptr

[HomuHomu833]

I encountered this issue while compiling in Lime, so I would like to submit a PR to fix this issue.

[tobil4sk]

I think profile.c is part of the hl binary, which is currently not possible to compile on arm64 anyway (it would require #895).

[HomuHomu833]

indeed but I can compile hl for aarch64 and even use Lime to build FNF. I think Lime only suffers from this

feel free to close the PR if needed I guess then.

[tobil4sk]

Lime should be modified to omit the hl binary if targetting arm64 and to only support hlc for arm64. Once proper arm64 support is added to hashlink jit then this issue will be solved.

[HomuHomu833]

will wait #895