m/b/fwprune: init

This adds a utility to filter out firmware that's actually used by the
kernel builtins.

Change-Id: If622ee8c5b056c9a75f1ca97bb1e40ae62cdf722
Reviewed-on: https://review.monogon.dev/c/monogon/+/506
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/metropolis/build/fwprune/BUILD.bazel b/metropolis/build/fwprune/BUILD.bazel
new file mode 100644
index 0000000..55aa5c5
--- /dev/null
+++ b/metropolis/build/fwprune/BUILD.bazel
@@ -0,0 +1,14 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["main.go"],
+    importpath = "source.monogon.dev/metropolis/build/fwprune",
+    visibility = ["//visibility:private"],
+)
+
+go_binary(
+    name = "fwprune",
+    embed = [":go_default_library"],
+    visibility = ["//visibility:public"],
+)