compile/compile.c had its own cleanup to unlink a file. This patch
replaces this cleanup with gdb::unlinker.
ChangeLog
2017-08-03 Tom Tromey <tom@tromey.com>
* compile/compile.c (cleanup_unlink_file): Remove.
(compile_to_object): Use gdb::unlinker.
(eval_compile_command): Likewise.