Remove build system name from deterministic dumps
* configure.ac (DETERMINISTIC_DUMP): New configuration option.
* lisp/version.el (emacs-build-time): Add a comment to make the
build time deterministic if requested.
(emacs-build-system): Make variable deterministic if requested.
* src/emacs.c (main): Initialize `deterministic-dump' from the
configuration option.
(syms_of_emacs): New constant `deterministic-dump'.
* src/sysdep.c (init_system_name): Use a constant
if a deterministic dump is requested.