AArch64: Eliminate crash in DEBUG build
AArch64: Eliminate crash in DEBUG build

In the DEBUG build, the contents of the X registers are either in
memory or in CPU registers, never both. After entering run-time
mode they are in memory, and their corresponding backing CPU
registers contains THE_NON_VALUE.

Therefore, we must enter run-time after the last use of the `ctx.reg`
register (which could a CPU register corresponding to a X register).

potatosalad/otp,erlang/otp,emacsmirror/erlang,vinoski/otp,bjorng/otp,vinoski/otp,potatosalad/otp,emacsmirror/erlang,dgud/otp,vinoski/otp,dgud/otp,emacsmirror/erlang,erlang/otp,bjorng/otp,vinoski/otp,vinoski/otp,potatosalad/otp,emacsmirror/erlang,potatosalad/otp,vinoski/otp,bjorng/otp,emacsmirror/erlang,bjorng/otp,dgud/otp,potatosalad/otp,emacsmirror/erlang,potatosalad/otp,erlang/otp,erlang/otp,dgud/otp,dgud/otp,erlang/otp,dgud/otp,vinoski/otp,emacsmirror/erlang,erlang/otp,emacsmirror/erlang,bjorng/otp,bjorng/otp,bjorng/otp,potatosalad/otp,bjorng/otp,emacsmirror/erlang,dgud/otp,vinoski/otp,potatosalad/otp,vinoski/otp,dgud/otp,erlang/otp,vinoski/otp,potatosalad/otp,dgud/otp,bjorng/otp,bjorng/otp,erlang/otp,emacsmirror/erlang,dgud/otp,erlang/otp,potatosalad/otp,erlang/otp