Use #$ for lambda fixups in native compilation data vectors

The "#$" syntax is recognized by Fread, which substitutes
Vload_file_name in its place.  If Vload_file_name is bound
appropriately, no other value can produce an object EQ to the one
produced by "#$".

We use this to check the data vector for entries that we know should
have been initialized: if the value is still equal to what we bound
Vload_file_name to when it was read, it wasn't initialized, and we
abort.

* lisp/emacs-lisp/comp.el (comp--#$): New defvar.
(comp--finalize-container): Use it.
* src/comp.c (ABI_VERSION): Bump.
(emit_static_object): Ensure 'comp--#$' prints as "#$".
(load_static_obj): Ensure '#$' reads as Vcomp__hashdollar.
(check_comp_unit_relocs): Adjust assertion.
(syms_of_comp): Define 'comp--#$'.
* src/pdumper.c (dump_do_dump_relocation): Adjust assertion.

lisp/emacs-lisp/comp.el

@@ -42,6 +42,7 @@
 (defvar comp-subr-arities-h)
 (defvar native-comp-eln-load-path)
 (defvar native-comp-enable-subr-trampolines)
+(defvar comp--\#$)
 
 (declare-function comp--compile-ctxt-to-file0 "comp.c")
 (declare-function comp--init-ctxt "comp.c")
@@ -3254,10 +3255,9 @@ Set it into the `type' slot."
                  ;; from the corresponding m-var.
                  collect (if (gethash obj
                                       (comp-ctxt-byte-func-to-func-h comp-ctxt))
-                             ;; Hack not to have `--lambda-fixup' in
-                             ;; data relocations as it would trigger the
-                             ;; check in 'check_comp_unit_relocs'.
-                             (intern (concat (make-string 1 ?-) "-lambda-fixup"))
+                             ;; This prints as #$, so we can assert this
+                             ;; value does not remain in the data vector
+                             comp--\#$
                            obj))))
 
 (defun comp--finalize-relocs ()