Add rootwait to grub command line to fix USB boot failures

Without this, one of my boards fails to reboot from USB drive due to
slow USB enumeration. Rootwait is not needed during the Fiwix -> Linux
jump, because we use an initramfs there, and the init scripts already
wait for USB drives to show up. Linux->Linux kexec, used with a custom
early kernel, might need it, so add it there as well to be safe.

steps/improve/make_bootable.sh

@@ -28,7 +28,7 @@ menuentry 'Linux live-bootstrap' {
     insmod part_msdos
     set root='$(grub-probe -d /dev/${DISK} -t bios_hints | sed -e 's/ //g')'
     set gfxpayload=auto
-    linux /boot/vmlinuz root=/dev/${DISK} rw $(cat /proc/cmdline)
+    linux /boot/vmlinuz root=/dev/${DISK} rootwait rw $(cat /proc/cmdline)
 }
 EOF
 

steps/jump/linux.sh

@@ -23,10 +23,10 @@ else
     # kexec time
     if [ "${BARE_METAL}" = True ]; then
         kexec -l "/boot/vmlinuz" \
-            --append="root=/dev/sda1 rootfstype=ext3 init=/init rw"
+            --append="root=/dev/sda1 rootfstype=ext3 init=/init rw rootwait"
     else
         kexec -l "/boot/vmlinuz" --console-serial \
-            --append="console=ttyS0 root=/dev/sda1 rootfstype=ext3 init=/init rw"
+            --append="console=ttyS0 root=/dev/sda1 rootfstype=ext3 init=/init rw rootwait"
     fi
     kexec -e
 fi