bootloader: Use 'invoke/quiet' when running 'grub-install' and co.

This hides potentially confusing GRUB messages from the user, such as
"Installing for i386-pc platform."

* gnu/bootloader/extlinux.scm (install-extlinux): Use 'invoke/quiet'
instead of 'system*' and 'error'.
* gnu/bootloader/grub.scm (install-grub, install-grub-efi): Likewise.
* guix/scripts/system.scm (bootloader-installer-script): Guard against
'message-condition?' and handle them properly.

1 files changed, 3 insertions, 5 deletions

diff --git a/gnu/bootloader/extlinux.scm b/gnu/bootloader/extlinux.scm
index 2bb711eed13..40108584a8f 100644
--- a/gnu/bootloader/extlinux.scm
+++ b/gnu/bootloader/extlinux.scm
@@ -91,11 +91,9 @@ TIMEOUT ~a~%"
         (for-each (lambda (file)
                     (install-file file install-dir))
                   (find-files syslinux-dir "\\.c32$"))
-        (unless
-            (and (zero? (system* extlinux "--install" install-dir))
-                 (write-file-on-device
-                  (string-append syslinux-dir "/" #$mbr) 440 device 0))
-          (error "failed to install SYSLINUX")))))
+        (invoke/quiet extlinux "--install" install-dir)
+        (write-file-on-device (string-append syslinux-dir "/" #$mbr)
+                              440 device 0))))
 
 (define install-extlinux-mbr
   (install-extlinux "mbr.bin"))