tool: introduce --target-system to choose target architecture

We will hard fail in case of encountering different architectures in bootspec.
This should still be compatible with cross-compiling systems in the future.

nix/modules/lanzaboote.nix

@@ -104,6 +104,7 @@ in
         ''}
 
         ${cfg.package}/bin/lzbt install \
+          --system ${config.nixpkgs.hostPlatform.system} \
           --systemd ${config.systemd.package} \
           --systemd-boot-loader-config ${loaderConfigFile} \
           --public-key ${cfg.publicKeyFile} \

rust/tool/shared/src/esp.rs

@@ -76,6 +76,7 @@ impl EspGenerationPaths {
     pub fn new<const N: usize, P: EspPaths<N>>(
         esp_paths: &P,
         generation: &Generation,
+        system: Architecture,
     ) -> Result<Self> {
         let bootspec = &generation.spec.bootspec.bootspec;
         let bootspec_system: Architecture = Architecture::from_nixos_system(&bootspec.system)?;

rust/tool/systemd/src/cli.rs

@@ -3,6 +3,7 @@ use std::path::PathBuf;
 use anyhow::{Context, Result};
 use clap::{Parser, Subcommand};
 
+use crate::esp::Architecture;
 use crate::install;
 use lanzaboote_tool::signature::KeyPair;
 
@@ -30,6 +31,10 @@ enum Commands {
 
 #[derive(Parser)]
 struct InstallCommand {
+    /// Target system
+    #[arg(long)]
+    target_system: String,
+
     /// Systemd path
     #[arg(long)]
     systemd: PathBuf,
@@ -90,6 +95,7 @@ fn install(args: InstallCommand) -> Result<()> {
 
     install::Installer::new(
         PathBuf::from(lanzaboote_stub),
+        Architecture::from_nixos_system(&args.target_system)?,
         args.systemd,
         args.systemd_boot_loader_config,
         key_pair,

rust/tool/systemd/src/install.rs

@@ -30,11 +30,13 @@ pub struct Installer {
     configuration_limit: usize,
     esp_paths: SystemdEspPaths,
     generation_links: Vec<PathBuf>,
+    arch: Architecture,
 }
 
 impl Installer {
     pub fn new(
         lanzaboote_stub: PathBuf,
+        arch: Architecture,
         systemd: PathBuf,
         systemd_boot_loader_config: PathBuf,
         key_pair: KeyPair,
@@ -56,6 +58,7 @@ impl Installer {
             configuration_limit,
             esp_paths,
             generation_links,
+            arch,
         }
     }
 
@@ -238,7 +241,7 @@ impl Installer {
 
         let bootspec = &generation.spec.bootspec.bootspec;
 
-        let esp_gen_paths = EspGenerationPaths::new(&self.esp_paths, generation)?;
+        let esp_gen_paths = EspGenerationPaths::new(&self.esp_paths, generation, self.arch)?;
         self.gc_roots.extend(esp_gen_paths.to_iter());
 
         let initrd_content = fs::read(
@@ -284,7 +287,7 @@ impl Installer {
 
         let bootspec = &generation.spec.bootspec.bootspec;
 
-        let esp_gen_paths = EspGenerationPaths::new(&self.esp_paths, generation)?;
+        let esp_gen_paths = EspGenerationPaths::new(&self.esp_paths, generation, self.arch)?;
 
         let kernel_cmdline =
             assemble_kernel_cmdline(&bootspec.init, bootspec.kernel_params.clone());