Support specifying arbitrary shell command in recipes

package-build.el

@@ -195,6 +195,12 @@ Note that Melpa leaves this disabled."
   :group 'package-build
   :type 'boolean)
 
+(defcustom package-build-run-recipe-shell-command nil
+  "Whether to run the shell command from the `:shell-command' recipe slot.
+Note that Melpa leaves this disabled."
+  :group 'package-build
+  :type 'boolean)
+
 (defcustom package-build-run-recipe-make-targets nil
   "Whether to run the make targets from the `:make-targets' recipe slot.
 Note that Melpa leaves this disabled."
@@ -1478,6 +1484,11 @@ in `package-build-archive-dir'."
     (unwind-protect
         (progn
           (funcall package-build-checkout-function rcp)
+          (when-let* ((package-build-run-recipe-shell-command)
+                      (command (oref rcp shell-command)))
+            (package-build--message "Running %s" command)
+            (package-build--call-sandboxed
+             rcp shell-file-name shell-command-switch command))
           (when-let ((package-build-run-recipe-make-targets)
                      (targets (oref rcp make-targets)))
             (package-build--message "Running make %s" (string-join targets " "))

package-recipe.el

@@ -52,6 +52,7 @@
    (time                                     :initform nil)
    (version                                  :initform nil)
    (version-regexp  :initarg :version-regexp :initform nil)
+   (shell-command   :initarg :shell-command  :initform nil)
    (make-targets    :initarg :make-targets   :initform nil)
    (org-exports     :initarg :org-exports    :initform nil)
    (old-names       :initarg :old-names      :initform nil))
@@ -171,7 +172,8 @@ file is invalid, then raise an error."
                name ident)
     (cl-assert plist)
     (let* ((symbol-keys '(:fetcher))
-           (string-keys '(:url :repo :commit :branch :version-regexp))
+           (string-keys '( :url :repo :commit :branch
+                           :version-regexp :shell-command))
            (list-keys '(:files :make-targets :org-exports :old-names))
            (all-keys (append symbol-keys string-keys list-keys)))
       (dolist (thing plist)