system: Delete current-system.new before attempting symlink.

If the system crashes after `current-system.new' is created,
but before it is renamed, then the system becomes unbootable,
as `symlink' will throw an error during activation.

This patch removes the .new symlink, if it exists,
before trying to create it anew.

* gnu/build/activation.scm (activate-current-system):
  Delete `.new' symlink if it exists, before trying to recreate it.

Merges: https://codeberg.org/guix/guix/pulls/9501
Signed-off-by: Nguyễn Gia Phong <cnx@loang.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/gnu/build/activation.scm b/gnu/build/activation.scm
index 53844c0990e..dbe35f41b88 100644
--- a/gnu/build/activation.scm
+++ b/gnu/build/activation.scm
@@ -497,6 +497,8 @@ improvement."
   (mkdir-p "/run")
   ;; Atomically make SYSTEM current.
   (let ((new (string-append %current-system ".new")))
+    (when (file-exists? new)
+      (delete-file new))
     (symlink system new)
     (rename-file new %current-system)))