installer: Add installer-specific run command process.

* gnu/installer/record.scm (installer)[run-command]: Add field.
* gnu/installer/utils.scm (run-command-in-installer): Add parameter.
* gnu/installer.scm (installer-program): Parameterize
run-command-in-installer with current installer's run-command.
* gnu/installer/newt.scm (newt-run-command): New variable.
(newt-installer): Use it.

Signed-off-by: Mathieu Othacehe <othacehe@gnu.org>

gnu/installer/utils.scm

@@ -25,6 +25,7 @@
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-19)
   #:use-module (srfi srfi-34)
+  #:use-module (srfi srfi-35)
   #:use-module (ice-9 control)
   #:use-module (ice-9 match)
   #:use-module (ice-9 popen)
@@ -39,6 +40,7 @@
             run-external-command-with-handler
             run-external-command-with-line-hooks
             run-command
+            run-command-in-installer
 
             syslog-port
             %syslog-line-hook
@@ -168,6 +170,14 @@ successfully, #f otherwise."
   (pause)
   succeeded?)
 
+(define run-command-in-installer
+  (make-parameter
+   (lambda (. args)
+     (raise
+      (condition
+       (&serious)
+       (&message (message "run-command-in-installer not set")))))))
+
 
 ;;;
 ;;; Logging.