treewide: move build helper to more fitting places

Change-Id: I3d0cfe9283222d403ae369ec9db09201ad511e15
Reviewed-on: https://review.monogon.dev/c/monogon/+/3327
Reviewed-by: Serge Bazanski <serge@monogon.tech>
Tested-by: Jenkins CI
diff --git a/metropolis/installer/main.go b/metropolis/installer/main.go
index bc428a0..e2d0d55 100644
--- a/metropolis/installer/main.go
+++ b/metropolis/installer/main.go
@@ -34,8 +34,8 @@
 
 	"golang.org/x/sys/unix"
 
-	"source.monogon.dev/metropolis/node/build/mkimage/osimage"
 	"source.monogon.dev/osbase/blockdev"
+	"source.monogon.dev/osbase/build/mkimage/osimage"
 	"source.monogon.dev/osbase/efivarfs"
 	"source.monogon.dev/osbase/sysfs"
 )