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/node/core/abloader/BUILD.bazel b/metropolis/node/core/abloader/BUILD.bazel
index d56a391..e8c49ac 100644
--- a/metropolis/node/core/abloader/BUILD.bazel
+++ b/metropolis/node/core/abloader/BUILD.bazel
@@ -1,5 +1,5 @@
 load("@rules_rust//rust:defs.bzl", "rust_binary")
-load("//metropolis/node/build:def.bzl", "platform_transition_binary")
+load("//osbase/build:def.bzl", "platform_transition_binary")
 
 rust_binary(
     name = "abloader_bin",