[clang] [llvm] [AArch64][PAC] Sign block addresses used in indirectbr. (PR #97647)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

Please make sure you have a testcase for computing the difference between two blockaddresses (`void g(int*); int f() { static int x = &&A-&&B; A:g(&x);B:return x; }`).  Not sure how you should handle that case.

https://github.com/llvm/llvm-project/pull/97647