m/c/metroctl: add MVP disk/image-only installer

This adds a very minimalist metroctl install command.
Only supports boostrapping and a single owner key.
But good enough to set up a node.

Change-Id: I9306a054b9540a3a0c70621f3f5d9cb34fc18d14
Reviewed-on: https://review.monogon.dev/c/monogon/+/417
Reviewed-by: Mateusz Zalega <mateusz@monogon.tech>
diff --git a/build/fietsje/deps_monogon.go b/build/fietsje/deps_monogon.go
index 6d1ddda..54e7d94 100644
--- a/build/fietsje/deps_monogon.go
+++ b/build/fietsje/deps_monogon.go
@@ -121,6 +121,9 @@
 		"github.com/muesli/reflow",
 	)
 
+	// Used by metroctl to resolve XDG directories
+	p.collect("github.com/adrg/xdg", "v0.4.0")
+
 	// First generate the repositories starlark rule into memory. This is because
 	// rendering will lock all unlocked dependencies, which might take a while. If a
 	// use were to interrupt it now, they would end up with an incomplete