Fix some compilation warnings in non nativecomp build (bug#43892)

* lisp/emacs-lisp/advice.el (comp-subr-trampoline-install):
	Declare function.
	* lisp/emacs-lisp/find-func.el (comp-eln-to-el-h): Declare
	variable.
	* lisp/emacs-lisp/nadvice.el (comp-subr-trampoline-install):
	Declare function.
	* lisp/files.el (comp-eln-to-el-h): Declare variable.
	* lisp/help.el (subr-native-lambda-list): Declare function.

lisp/emacs-lisp/advice.el

@@ -2052,6 +2052,8 @@ in that CLASS."
 		 function class name)))
     (error "ad-remove-advice: `%s' is not advised" function)))
 
+(declare-function comp-subr-trampoline-install "comp")
+
 ;;;###autoload
 (defun ad-add-advice (function advice class position)
   "Add a piece of ADVICE to FUNCTION's list of advices in CLASS.

lisp/emacs-lisp/find-func.el

@@ -178,6 +178,8 @@ See the functions `find-function' and `find-variable'."
             (setq name rel))))
     (unless (equal name library) name)))
 
+(defvar comp-eln-to-el-h)
+
 (defun find-library-name (library)
   "Return the absolute file name of the Emacs Lisp source of LIBRARY.
 LIBRARY should be a string (the name of the library)."

lisp/emacs-lisp/nadvice.el

@@ -316,6 +316,8 @@ is also interactive.  There are 3 cases:
   `(advice--add-function ,where (gv-ref ,(advice--normalize-place place))
                          ,function ,props))
 
+(declare-function comp-subr-trampoline-install "comp")
+
 ;;;###autoload
 (defun advice--add-function (where ref function props)
   (when (and (featurep 'nativecomp)

lisp/files.el

@@ -900,6 +900,8 @@ recursion."
 		       (read-file-name "Load file: " nil nil 'lambda))))
   (load (expand-file-name file) nil nil t))
 
+(defvar comp-eln-to-el-h)
+
 (defun locate-file (filename path &optional suffixes predicate)
   "Search for FILENAME through PATH.
 If found, return the absolute file name of FILENAME; otherwise

lisp/help.el

@@ -1320,6 +1320,8 @@ ARGLIST can also be t or a string of the form \"(FUN ARG1 ARG2 ...)\"."
                   (error "Unrecognized usage format"))
 	      (help--make-usage-docstring 'fn arglist)))))
 
+(declare-function subr-native-lambda-list "data.c")
+
 (defun help-function-arglist (def &optional preserve-names)
   "Return a formal argument list for the function DEF.
 If PRESERVE-NAMES is non-nil, return a formal arglist that uses