fix(zbm): Use a known good stub loader file (#3)

This works around https://github.com/zbm-dev/zfsbootmenu/issues/503

setup.sh

@@ -566,6 +566,7 @@ EFI:
   ImageDir: /efi/EFI/ZBM
   Versions: 1
   Enabled: true
+  Stub: /etc/zfsbootmenu/stub-loader.d/linuxx64.efi.stub
 Kernel:
   CommandLine: ro loglevel=0 zbm.import_policy=hostid
   Prefix: vmlinuz
@@ -574,6 +575,14 @@ EOF
     zfs set org.zfsbootmenu:commandline='rw nowatchdog rd.vconsole.keymap=de-latin1' "${zpool_name}"'/root/'"${zfs_arch_dataset_name}"
 }
 
+function get_known_good_stub_loader () {
+    local known_good_stub_loader local_stub_loader_abs
+    known_good_stub_loader='https://github.com/zbm-dev/zfsbootmenu/raw/master/testing/stubs/linuxx64.efi.stub'
+    local local_stub_loader_abs='/etc/zfsbootmenu/stub-loader.d/linuxx64.efi.stub'
+    mkdir -p "$(dirname "${local_stub_loader_abs}")"
+    curl --silent --location "${known_good_stub_loader}" --output "${local_stub_loader_abs}"
+}
+
 function get_disks_with_one_efipart () {
     local disks_with_one_efipart
     # Find disks that have exactly one EFI partition and where that EFI
@@ -613,6 +622,7 @@ function install_os_in_chroot () {
 
     # Install ZFSBootMenu image
     configure_zfsbootmenu                       #2.9
+    get_known_good_stub_loader                  #2.10
     generate-zbm
 }