install: Support bootloader install config options

This allows you to set a non-default ostree bootloader backend.
In particular, this is needed for aboot images, as otherwise
the deploy will not shell out to aboot-deploy to create the required
A/B boot symlinks.

Author: alexlarsson

crates/lib/src/install.rs

@@ -624,6 +624,24 @@ async fn initialize_ostree_root(state: &State, root_setup: &RootSetup) -> Result
             .run_capture_stderr()?;
     }
 
+    if let Some(install_config) = &state.install_config {
+        if let Some(bootloader) = &install_config.bootloader {
+            tracing::debug!("Setting bootloader to {bootloader}");
+            Command::new("ostree")
+                .args([
+                    "config",
+                    "--repo",
+                    "ostree/repo",
+                    "set",
+                    "sysroot.bootloader",
+                    &bootloader,
+                ])
+                .cwd_dir(rootfs_dir.try_clone()?)
+                .run_capture_stderr()
+                .context("Setting bootloader config")?;
+        }
+    }
+
     let sysroot = {
         let path = format!(
             "/proc/{}/fd/{}",

crates/lib/src/install/config.rs

@@ -73,6 +73,8 @@ pub(crate) struct InstallConfiguration {
     pub(crate) kargs: Option<Vec<String>>,
     /// Supported architectures for this configuration
     pub(crate) match_architectures: Option<Vec<String>>,
+    /// Bootloader backend to use
+    pub(crate) bootloader: Option<String>,
 }
 
 fn merge_basic<T>(s: &mut Option<T>, o: Option<T>, _env: &EnvProperties) {
@@ -138,6 +140,7 @@ impl Mergeable for InstallConfiguration {
                     .get_or_insert_with(Default::default)
                     .extend(other_kargs)
             }
+            merge_basic(&mut self.bootloader, other.bootloader, env);
         }
     }
 }
@@ -276,6 +279,7 @@ root-fs-type = "xfs"
             r##"[install]
 root-fs-type = "ext4"
 kargs = ["console=ttyS0", "foo=bar"]
+bootloader = "aboot"
 "##,
         )
         .unwrap();
@@ -302,7 +306,8 @@ kargs = ["console=ttyS0", "foo=bar"]
                     .map(ToOwned::to_owned)
                     .collect()
             )
-        )
+        );
+        assert_eq!(install.bootloader, Some("aboot".to_string()));
     }
 
     #[test]