m/n/b/fwprune: adapt to fsspec and use

This modifies the fwprune tool to generate fsspecs instead of making
copies and makes it take a list of paths for suffix matching instead
of a directory as input. It also adds the fsspec_linux_firmware rule
which uses the utility to actually build a partial fsspec. Finally it
integrates the linux-firmware external repository and uses that rule
to ship firmware in Metropolis.

Change-Id: I0552995105eda84e63d7259040ad36d794079308
Reviewed-on: https://review.monogon.dev/c/monogon/+/534
Reviewed-by: Mateusz Zalega <mateusz@monogon.tech>
diff --git a/metropolis/node/BUILD.bazel b/metropolis/node/BUILD.bazel
index 722f05b..72a8e11 100644
--- a/metropolis/node/BUILD.bazel
+++ b/metropolis/node/BUILD.bazel
@@ -1,6 +1,7 @@
 load("@io_bazel_rules_go//go:def.bzl", "go_library")
 load("//metropolis/node/build:def.bzl", "erofs_image", "verity_image")
 load("//metropolis/node/build:efi.bzl", "efi_unified_kernel_image")
+load("//metropolis/node/build/fwprune:def.bzl", "fsspec_linux_firmware")
 load("@rules_pkg//:pkg.bzl", "pkg_zip")
 
 go_library(
@@ -21,6 +22,12 @@
     },
 )
 
+fsspec_linux_firmware(
+    name = "firmware",
+    firmware_files = ["@linux-firmware//:all_files"],
+    kernel = "//third_party/linux",
+)
+
 erofs_image(
     name = "rootfs",
     extra_dirs = [
@@ -86,6 +93,7 @@
         "@xfsprogs//:mkfs": "/bin/mkfs.xfs",
         "@chrony//:chrony": "/time/chrony",
     },
+    fsspecs = [":firmware"],
     symlinks = {
         "/ephemeral/machine-id": "/etc/machine-id",
         "/ephemeral/hosts": "/etc/hosts",