build/fietsje: move to toolbase

This removes some of the bash magic copied over from Gazelle, and
instead uses toolbase to achieve the same effect.

Change-Id: I6ea3bfda68092c00ea58883bb9b1f7c0779a97e6
Reviewed-on: https://review.monogon.dev/c/monogon/+/330
Reviewed-by: Mateusz Zalega <mateusz@monogon.tech>
diff --git a/BUILD b/BUILD
index 003b71f..2b9c78c 100644
--- a/BUILD
+++ b/BUILD
@@ -1,5 +1,4 @@
 load("@bazel_gazelle//:def.bzl", "gazelle")
-load("//build/fietsje:def.bzl", "fietsje")
 load("@io_bazel_rules_go//go:def.bzl", "go_path")
 
 # gazelle:prefix source.monogon.dev
@@ -7,7 +6,10 @@
 # gazelle:go_naming_convention_external go_default_library
 gazelle(name = "gazelle")
 
-fietsje(name = "fietsje")
+alias(
+    name = "fietsje",
+    actual = "//build/fietsje",
+)
 
 # Shortcut for the Go SDK
 alias(