install: Error out early on s390x

xref coreos/bootupd#550

Signed-off-by: Colin Walters <[email protected]>

Author: cgwalters

lib/src/install.rs

@@ -790,6 +790,10 @@ async fn prepare_install(
     crate::cli::require_root()?;
     require_systemd_pid1()?;
 
+    if cfg!(target_arch = "s390x") {
+        anyhow::bail!("Installation is not supported on this architecture yet");
+    }
+
     let rootfs = cap_std::fs::Dir::open_ambient_dir("/", cap_std::ambient_authority())
         .context("Opening /")?;