Fix dumping on GNU/Linux ppc64le

Fix dumping on GNU/Linux ppc64le

Problem reported by Thomas Fitzsimmons (Bug#33174).
* src/emacs.c (main): Adjust to sysdep.c changes.
* src/sysdep.c (exec_personality): New static var.
(disable_address_randomization): Remove, replacing with ...
(maybe_disable_address_randomization): ... this new function.
Do not set or use an environment variable; use a command-line
argument instead, and set the new static var.  Migrate the emacs.c
personality-change code to here, where it belongs.
(emacs_exec_file): Simplify by using new static var.