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/test/run_test.go b/metropolis/installer/test/run_test.go
index fef8e20..64fa210 100644
--- a/metropolis/installer/test/run_test.go
+++ b/metropolis/installer/test/run_test.go
@@ -38,7 +38,7 @@
 	"source.monogon.dev/metropolis/proto/api"
 
 	mctl "source.monogon.dev/metropolis/cli/metroctl/core"
-	"source.monogon.dev/metropolis/node/build/mkimage/osimage"
+	"source.monogon.dev/osbase/build/mkimage/osimage"
 	"source.monogon.dev/osbase/cmd"
 )