Temporary fix for debian7 (elastic#11768)

(cherry picked from commit 6f1f994)

x-pack/auditbeat/magefile.go

@@ -262,7 +262,11 @@ func installDependencies(pkg, arch string) error {
  }
  }
 
- if err := sh.Run("apt-get", "update"); err != nil {
+ // TODO: This is only for debian 7 and should be removed when move to a newer OS. This flag is
+ // going to be used unnecessary when building using non-debian7 images
+ // (like when making the linux/arm binaries) and we should remove it soonish.
+ // See https://github.com/elastic/beats/issues/11750 for more details.
+ if err := sh.Run("apt-get", "update", "-o", "Acquire::Check-Valid-Until=false"); err != nil {
  return err
  }