[libunwind][PAC] Defang ptrauth's PC in valid CFI range abort (#184041)
It turns out making the CFI check a release mode abort causes many, if
not the majority, of JITs to fail during unwinding as they do not set up
CFI sections for their generated code. As a result any JITs that do
nominally support unwinding (and catching) through their JIT or assembly
frames trip this abort.
rdar://170862047