Support native compilation of packages on install

* lisp/emacs-lisp/package.el (package-unpack)
(package--native-compile): Native compile packages on install, if the
feature is available.  (Bug#44676)
(package-native-compile): New defcustom.

lisp/emacs-lisp/package.el

@@ -389,6 +389,12 @@ a sane initial value."
   :version "25.1"
   :type '(repeat symbol))
 
+(defcustom package-native-compile nil
+  "Non-nil means to native compile packages on installation."
+  :type '(boolean)
+  :risky t
+  :version "28.1")
+
 (defcustom package-menu-async t
   "If non-nil, package-menu will use async operations when possible.
 Currently, only the refreshing of archive contents supports
@@ -968,6 +974,8 @@ untar into a directory named DIR; otherwise, signal an error."
         ;; E.g. for multi-package installs, we should first install all packages
         ;; and then compile them.
         (package--compile new-desc)
+        (when package-native-compile
+          (package--native-compile-async new-desc))
         ;; After compilation, load again any files loaded by
         ;; `activate-1', so that we use the byte-compiled definitions.
         (package--load-files-for-activation new-desc :reload)))
@@ -1052,6 +1060,15 @@ This assumes that `pkg-desc' has already been activated with
         (load-path load-path))
     (byte-recompile-directory (package-desc-dir pkg-desc) 0 t)))
 
+(defun package--native-compile-async (pkg-desc)
+  "Native compile installed package PKG-DESC asynchronously.
+This assumes that `pkg-desc' has already been activated with
+`package-activate-1'."
+  (when (and (featurep 'nativecomp)
+             (native-comp-available-p))
+    (let ((warning-minimum-level :error))
+      (native-compile-async (package-desc-dir pkg-desc) t))))
+
 ;;;; Inferring package from current buffer
 (defun package-read-from-string (str)
   "Read a Lisp expression from STR.