Comment 9 for bug 1779815

The following hack resolves the issue for me on arm64:

--- build/util/grub-gencfg.orig 2018-07-17 23:19:53.101127509 +0000
+++ build/util/grub-gencfg 2018-07-17 22:44:09.465555019 +0000
@@ -144,6 +144,7 @@
     push @cmdline, @OPTS;
     push @cmdline, "rescue/enable=true" if $xattr{Rescue};
     push @cmdline, "speakup.synth=soft" if $xattr{Speach};
+ push @cmdline, "scsi_mod.scan=sync";
     push @cmdline, "---";
     push @cmdline, "quiet" if $xattr{Quiet};